export SwipeableListView component.

Summary:
Explain the **motivation** for making this change. What existing problem does the pull request solve?

1. [`SwipeableListView`](https://github.com/facebook/react-native/blob/master/Libraries/Experimental/SwipeableRow/SwipeableListView.js) is already usable, I think it would be great to export it so users can test it.
Closes https://github.com/facebook/react-native/pull/8482

Differential Revision: D3542403

Pulled By: fred2028

fbshipit-source-id: 7b4e0aa8c50110e434c9d64b72b15d1206fa0470

Libraries/react-native/react-native.js

@@ -54,6 +54,7 @@ const ReactNative = {
   get RecyclerViewBackedScrollView() { return require('RecyclerViewBackedScrollView'); },
   get RefreshControl() { return require('RefreshControl'); },
   get StatusBar() { return require('StatusBar'); },
+  get SwipeableListView() { return require('SwipeableListView'); },
   get SwitchAndroid() { return require('SwitchAndroid'); },
   get SwitchIOS() { return require('SwitchIOS'); },
   get TabBarIOS() { return require('TabBarIOS'); },

Libraries/react-native/react-native.js.flow

@@ -63,6 +63,7 @@ var ReactNative = {
   Slider: require('Slider'),
   SnapshotViewIOS: require('SnapshotViewIOS'),
   StatusBar: require('StatusBar'),
+  SwipeableListView: require('SwipeableListView'),
   Switch: require('Switch'),
   RecyclerViewBackedScrollView: require('RecyclerViewBackedScrollView'),
   RefreshControl: require('RefreshControl'),