Fallback to ScrollView on ios

Fix cesardeazevedo#11

Author: cesardeazevedo

index.js

@@ -1,2 +1,7 @@
+import { Platform, ScrollView } from 'react-native';
 import NestedScrollView from './lib/NestedScrollView';
-export default NestedScrollView;
+
+export default Platform.select({
+  ios: ScrollView,
+  android: NestedScrollView
+})