Update references to `image!` to use require syntax

Summary: Closes https://github.com/facebook/react-native/pull/5089

Reviewed By: svcscm

Differential Revision: D2798548

Pulled By: androidtrunkagent

fb-gh-sync-id: 9e561fcfc103102d4c4bfbebc463eadb2fdd561a

Libraries/Image/Image.ios.js

@@ -46,7 +46,7 @@ var {
  *     <View>
  *       <Image
  *         style={styles.icon}
- *         source={require('image!myIcon')}
+ *         source={require('./myIcon.png')}
  *       />
  *       <Image
  *         style={styles.logo}
@@ -63,7 +63,7 @@ var Image = React.createClass({
     /**
      * `uri` is a string representing the resource identifier for the image, which
      * could be an http address, a local file path, or the name of a static image
-     * resource (which should be wrapped in the `require('image!name')` function).
+     * resource (which should be wrapped in the `require('./path/to/image.png')` function).
      */
     source: PropTypes.oneOfType([
       PropTypes.shape({