Upgrade the ReduxExample app (use CRNA) (#2171)

* [ReduxExample] Delete android and ios dirs

* [ReduxExample] Upgrade using create-react-native-app

* [ReduxExample] Add postinstall script to clean up files Yarn copies in

Yarn copies them when installing locally, causing lots of @proviesModule collisions.

* [ReduxExample] Upgrade expo and other dependencies

* [ReduxExample] Don't delete .git just in case

examples/ReduxExample/App.js

@@ -0,0 +1,27 @@
+/**
+ * @flow
+ */
+
+import React from 'react';
+import { AppRegistry } from 'react-native';
+import { Provider } from 'react-redux';
+import { createStore } from 'redux';
+
+import AppReducer from './src/reducers';
+import AppWithNavigationState from './src/navigators/AppNavigator';
+
+class ReduxExampleApp extends React.Component {
+  store = createStore(AppReducer);
+
+  render() {
+    return (
+      <Provider store={this.store}>
+        <AppWithNavigationState />
+      </Provider>
+    );
+  }
+}
+
+AppRegistry.registerComponent('ReduxExample', () => ReduxExampleApp);
+
+export default ReduxExampleApp;