Remove ReactNative.Children is deprecated warning (#7)

* switch React reference from React Native to  React for iOS

* switch React reference from React Native to React for android

Author: James

ActionSheet.android.js

@@ -1,11 +1,14 @@
 'use strict';
 
 import React, {
+  PropTypes,
+} from 'react';
+
+import {
   Animated,
   BackAndroid,
   Easing,
   PixelRatio,
-  PropTypes,
   StyleSheet,
   Text,
   TouchableOpacity,

ActionSheet.ios.js

@@ -1,6 +1,7 @@
 'use strict';
 
-import React, {
+import React from 'react';
+import {
   ActionSheetIOS,
   View,
 } from 'react-native';