This PR fixes two crashes when enableWebKit is true (which was the default) on iOS 9.x. The first one when the WebView component was mounted (fixes issue #150) and the second one, when the component was unmounted (fixes issue #213).

The first problem happen when the RNCWKWebView.m was loaded:

The programming guide for WebKit (version 2006) ([pdf](http://mirror.informatimago.com/next/developer.apple.com/documentation/Cocoa/Conceptual/DisplayWebContent/WebKit_DisplayWebContent.pdf)) from Apple said, that it is (was) required to check if the 'new' WebKit Framework was available. This was required when the WebKit framework was only available on Mac OS X (10.2) when the Safari was installed. 😆

Because WebKit is (currently..) a fix part of iOS we didn't need this check this anymore to determinate if WebKit is available. I also see no other reference that this is required in iOS so I just remove this code. Without this code the WebView works also on iOS 9.x.

The second issue happen when the WKWebView was removed from the native view hierarchy. Its required (only on iOS 9) to remove the UIScrollView delegate before cleaning up the webview.

Its possible to try this PR with:

```
npm install --save "react-native-webview@jerolimov/react-native-webview#fix-ios9-crash"
# or
yarn add "react-native-webview@jerolimov/react-native-webview#fix-ios9-crash"
```

If you use CocoaPods, you should also update your Pods with

```
cd ios && pod update && cd ..
```

# [5.2.0](https://github.com/react-native-community/react-native-webview/compare/v5.1.0...v5.2.0) (2019-02-12)

### Features

* **toggle scroll bar:** added new props showsVerticalScrollIndicator / showsHorizontalScrollIndicator ([#250](https://github.com/react-native-community/react-native-webview/issues/250)) ([92c2058](https://github.com/react-native-community/react-native-webview/commit/92c2058))

* docs: update README.md

* docs: update .all-contributorsrc

# [5.1.0](https://github.com/react-native-community/react-native-webview/compare/v5.0.8...v5.1.0) (2019-02-12)

### Features

* **wkwebview:** create api to allow clients to present a client credential for authentication ([#141](https://github.com/react-native-community/react-native-webview/issues/141)) ([fc5fd24](https://github.com/react-native-community/react-native-webview/commit/fc5fd24))

* In order for TLS Mutual Auth to work for webviews, the caller must present a credential. Expose a setter that can be called to set a credential.

## [5.0.8](https://github.com/react-native-community/react-native-webview/compare/v5.0.7...v5.0.8) (2019-02-11)

### Bug Fixes

* **types:** Add new cacheEnabled prop to typescript prop type declarations ([#335](https://github.com/react-native-community/react-native-webview/issues/335)) ([ff62c95](https://github.com/react-native-community/react-native-webview/commit/ff62c95))

* Deleted onShouldStartLoadWithRequest platform reference

according to b1b662628e it's supported on android and Ios so  no platfor reference is needed

* Deleted onShouldStartLoadWithRequest platform reference 

Now with added note

* docs: update README.md

* docs: update .all-contributorsrc

## [5.0.7](https://github.com/react-native-community/react-native-webview/compare/v5.0.6...v5.0.7) (2019-02-08)

### Bug Fixes

* **package.json:** Warning because peerDependencies >=0.57 <0.59 ([#279](https://github.com/react-native-community/react-native-webview/issues/279)) ([#327](https://github.com/react-native-community/react-native-webview/issues/327)) ([46286b2](https://github.com/react-native-community/react-native-webview/commit/46286b2))

## [5.0.6](https://github.com/react-native-community/react-native-webview/compare/v5.0.5...v5.0.6) (2019-02-06)

### Bug Fixes

* **WKWebView.m:** Reapplied [#134](https://github.com/react-native-community/react-native-webview/issues/134) with additional checks to tackle unintentional scrolls ([#296](https://github.com/react-native-community/react-native-webview/issues/296)) ([3f58b0e](https://github.com/react-native-community/react-native-webview/commit/3f58b0e))

## [5.0.5](https://github.com/react-native-community/react-native-webview/compare/v5.0.4...v5.0.5) (2019-02-05)

### Bug Fixes

* **iOS/android getViewManagerConfig:** Fix crash with react-native < 0.58 ([263fc5e](https://github.com/react-native-community/react-native-webview/commit/263fc5e))

## [5.0.4](https://github.com/react-native-community/react-native-webview/compare/v5.0.3...v5.0.4) (2019-02-04)

### Bug Fixes

* **UIWebview:** Deprecate UIWebView and add link to issue ([#313](https://github.com/react-native-community/react-native-webview/issues/313)) ([4c80240](https://github.com/react-native-community/react-native-webview/commit/4c80240))

* Update WebView.ios.js

* Update WebView.ios.js

## [5.0.3](https://github.com/react-native-community/react-native-webview/compare/v5.0.2...v5.0.3) (2019-02-04)

### Bug Fixes

* **android/iOS:** Fixed react-native 0.58 warnings ([#311](https://github.com/react-native-community/react-native-webview/issues/311)) ([4a4ccd8](https://github.com/react-native-community/react-native-webview/commit/4a4ccd8))

Adds @MalcolmScruggs as a contributor for code, tool, test.

This was requested by Titozzz [in this comment](https://github.com/react-native-community/react-native-webview/pull/293#issuecomment-460077647)

## [5.0.2](https://github.com/react-native-community/react-native-webview/compare/v5.0.1...v5.0.2) (2019-02-03)

### Bug Fixes

* **webviewShared.js:** Support all valid URI schemes and add testing ([#293](https://github.com/react-native-community/react-native-webview/issues/293)) ([fb78d13](https://github.com/react-native-community/react-native-webview/commit/fb78d13)), closes [/tools.ietf.org/html/rfc3986#section-3](https://github.com//tools.ietf.org/html/rfc3986/issues/section-3)

* Change origin whitelist to allow for all valid URIs

- Now supports +, -, and .
- Prevent whitelist from matching when preceded by unwanted characters
- URI must begin with letter
- URI Scheme syntax: https://tools.ietf.org/html/rfc3986#section-3.1

* Add jest testing framework and run it on CI

* Add tests for WebViewShared's createOnShouldStartLoadWithRequest

* docs: update README.md

* docs: update .all-contributorsrc

## [5.0.1](https://github.com/react-native-community/react-native-webview/compare/v5.0.0...v5.0.1) (2019-02-01)

### Bug Fixes

* **PostMessage:** Renamed ReactNativeWebview to ReactNativeWebView ([d5fc028](https://github.com/react-native-community/react-native-webview/commit/d5fc028)), closes [#304](https://github.com/react-native-community/react-native-webview/issues/304)

fixes #304

# [5.0.0](https://github.com/react-native-community/react-native-webview/compare/v4.1.0...v5.0.0) (2019-02-01)

### Features

* **Android/iOS postMessage:** refactoring the old postMessage implementation ([#303](https://github.com/react-native-community/react-native-webview/issues/303)) ([f3bdab5](https://github.com/react-native-community/react-native-webview/commit/f3bdab5)), closes [#29](https://github.com/react-native-community/react-native-webview/issues/29) [#272](https://github.com/react-native-community/react-native-webview/issues/272) [#221](https://github.com/react-native-community/react-native-webview/issues/221) [#105](https://github.com/react-native-community/react-native-webview/issues/105) [#66](https://github.com/react-native-community/react-native-webview/issues/66)

### BREAKING CHANGES

* **Android/iOS postMessage:** Communication from webview to react-native has been completely rewritten. React-native-webview will not use or override window.postMessage anymore. Reasons behind these changes can be found throughout so many issues that it made sense to go that way.

Instead of using window.postMessage(data, *), please now use window.ReactNativeWebView.postMessage(data).

Side note: if you wish to keep compatibility with the old version when you upgrade, you can use the injectedJavascript prop to do that:

const injectedJavascript = `(function() {
  window.postMessage = function(data) {
    window.ReactNativeWebView.postMessage(data);
  };
})()`;

Huge thanks to @jordansexton and @KoenLav!

fixes #29
fixes #272
fixes #221
fixes #105
fixes #66

BREAKING CHANGE: Communication from webview to react-native has been completely rewritten. React-native-webview will not use or override window.postMessage anymore. Reasons behind these changes can be found throughout so many issues that it made sense to go that way.

Instead of using window.postMessage(data, *), please now use window.ReactNativeWebView.postMessage(data).

Side note: if you wish to keep compatibility with the old version when you upgrade, you can use the injectedJavascript prop to do that:

const injectedJavascript = `(function() {
  window.postMessage = function(data) {
    window.ReactNativeWebView.postMessage(data);
  };
})()`;

Huge thanks to @jordansexton and @KoenLav!

# [4.1.0](https://github.com/react-native-community/react-native-webview/compare/v4.0.0...v4.1.0) (2019-02-01)

### Features

* **WKwebview:** Allow _target links to be opened up in the same way as UIWebView. ([#270](https://github.com/react-native-community/react-native-webview/issues/270)) ([6643a8e](https://github.com/react-native-community/react-native-webview/commit/6643a8e)), closes [#139](https://github.com/react-native-community/react-native-webview/issues/139)

Fixes #139

# [4.0.0](https://github.com/react-native-community/react-native-webview/compare/v3.2.2...v4.0.0) (2019-01-30)

### Features

* **iOS/Android:** Add `cacheEnabled` prop ([#152](https://github.com/react-native-community/react-native-webview/issues/152)) ([83ce79f](https://github.com/react-native-community/react-native-webview/commit/83ce79f))

### BREAKING CHANGES

* **iOS/Android:** This change makes caching enabled by default when previously there was no caching behavior which may cause unexpected behaviour changes in your existing implementations.

Added a new cacheEnabled prop to toggle Android & iOS webview caching behavior.

BREAKING CHANGE:  This change makes caching enabled by default when previously there was no caching behavior which may cause unexpected behaviour changes in your existing implementations.

Just a minor correction of the anchor link in Readme file.

## [3.2.2](https://github.com/react-native-community/react-native-webview/compare/v3.2.1...v3.2.2) (2019-01-29)

### Bug Fixes

* **android:** Fix Download on android P  ([#273](https://github.com/react-native-community/react-native-webview/issues/273)) ([15d904f](https://github.com/react-native-community/react-native-webview/commit/15d904f)), closes [#266](https://github.com/react-native-community/react-native-webview/issues/266)

Fixes #266. 
Now downloading works on Motorola Moto One with Android 9.

## [3.2.1](https://github.com/react-native-community/react-native-webview/compare/v3.2.0...v3.2.1) (2019-01-23)

### Bug Fixes

* **Gradle:** Allow kotlinVersion override using ext with gradle.properties ([#267](https://github.com/react-native-community/react-native-webview/issues/267)) ([2846e27](https://github.com/react-native-community/react-native-webview/commit/2846e27))

You can now override kotlin version by defining ext kotlinVersion

Adds @YangXiaomei as a contributor for code, doc.

This was requested by Titozzz [in this comment](https://github.com/react-native-community/react-native-webview/pull/265#issuecomment-456327682)

# [3.2.0](https://github.com/react-native-community/react-native-webview/compare/v3.1.3...v3.2.0) (2019-01-22)

### Features

* **android props:** Add `androidHardwareAccelerationDisabled` prop ([#265](https://github.com/react-native-community/react-native-webview/issues/265)) ([d3fc5e6](https://github.com/react-native-community/react-native-webview/commit/d3fc5e6))

* add test code for disable hardware acceleration

* add interface to disable android hardware acceleration

* Update index.d.ts

Adds @smathson as a contributor for code, doc.

This was requested by Titozzz [in this comment](https://github.com/react-native-community/react-native-webview/pull/203#issuecomment-455618880)

Adds @Salakar as a contributor for code, review, ideas, tool.

This was requested by Titozzz [in this comment](https://github.com/react-native-community/react-native-webview/pull/164#issuecomment-455618092)