Update README.md

Correct `CocoaPods` installation instructions.

README.md

 Or if using CocoaPods, add the pod to your `Podfile`, for example:
 
 ```
-pod 'react-native-fetch-blob,
-    :path => '../node_modules/react-native-fetch-blob
+pod 'react-native-fetch-blob',
+    :path => '../node_modules/react-native-fetch-blob'
 ```
 
 **Automatically Link Native Modules**