Update imports in generated projects

Summary:Fixes warnings when React API is used by requiring 'react-native'.
Closes https://github.com/facebook/react-native/pull/7060

Differential Revision: D3196109

Pulled By: mkonicek

fb-gh-sync-id: b47afc138cd7909ad53c0d67a65e3a124b87134b
fbshipit-source-id: b47afc138cd7909ad53c0d67a65e3a124b87134b

local-cli/generator/templates/index.android.js

@@ -3,9 +3,9 @@
  * https://github.com/facebook/react-native
  */
 
-import React, {
+import React, { Component } from 'react';
+import {
   AppRegistry,
-  Component,
   StyleSheet,
   Text,
   View

local-cli/generator/templates/index.ios.js

@@ -4,9 +4,9 @@
  * @flow
  */
 
-import React, {
+import React, { Component } from 'react';
+import {
   AppRegistry,
-  Component,
   StyleSheet,
   Text,
   View