* Add ability to set attributes of navigation bar buttons separately.

* Added ability to set button style when calling `setButtons` method.

* Add documentation.

fixes #942

* Send willAppear didAppear for initial screen

* empty commit

- compileSdkVersion 25
- buildToolsVersion "25.0.1"

Support status bar color in Modals

fixes #1034

* Support custom font in the Menu items.

* Fix check for custom font.

Add tabBarTranslucent style option in tabsStyle

This commit adds support for the following style properties:
titleBarTitleFontFamily - string, font name in assets
titleBarTitleTextCentered - boolean, default is false

* adding support for android centered title and custom font

* PR feedback

Support customize icon for left nav button in android

FadeIn ContentView and TopBar when pushing shared element screen

If the screen is pushed with `animated: false` then only TopBar is
animated in. This is a compromise until we expose means to control the
transition of each element on the screen.

Reading the docs I couldn't see a way to simply change the color of the status bar on Android. Only via https://github.com/wix/react-native-navigation/issues/571#issuecomment-267255350 I saw there was a prop to do this.

(Assuming this is Android only since iOS only allows for light or dark).

* Temporarily disable shared element screens in example app

* Fix card positioning when transitioning

* resolve rnn dep from npm