Support snapToInterval for horizontal scrollview on Android

Summary:
`snapToInterval` is available on iOS but on android yet. This PR is to add support for `snapToInterval` on android.

Example:

![android_snap](https://cloud.githubusercontent.com/assets/1699429/19086983/39d3ee1c-8a25-11e6-9c84-20f25a751f32.gif)

TO: lelandrichardson spikebrehm
Closes https://github.com/facebook/react-native/pull/10242

Differential Revision: D4168527

fbshipit-source-id: de3dd9ac5d9e0fddfce5e5bc0aa6a4f33f1e30b3

RNTester/js/ScrollViewSimpleExample.js

@@ -46,6 +46,20 @@ class ScrollViewSimpleExample extends React.Component<{}> {
         {this.makeItems(NUM_ITEMS, [styles.itemWrapper, styles.horizontalItemWrapper])}
       </ScrollView>
     );
+    items.push(
+      <ScrollView
+        key={'scrollViewSnap'}
+        horizontal
+        snapToInterval={210}
+        pagingEnabled
+      >
+        {this.makeItems(NUM_ITEMS, [
+          styles.itemWrapper,
+          styles.horizontalItemWrapper,
+          styles.horizontalPagingItemWrapper,
+        ])}
+      </ScrollView>
+    );
 
     var verticalScrollView = (
       <ScrollView style={styles.verticalScrollView}>
@@ -72,7 +86,10 @@ var styles = StyleSheet.create({
   },
   horizontalItemWrapper: {
     padding: 50
-  }
+  },
+  horizontalPagingItemWrapper: {
+    width: 200,
+  },
 });
 
 module.exports = ScrollViewSimpleExample;