TabBarIOS tintColor

Summary:
[Origin Pull request](https://github.com/facebook/react-native/pull/961) from [cmcewen](https://github.com/cmcewen)

All the work have been done by @cmcewen, I just rebased his work with the master.
Closes https://github.com/facebook/react-native/pull/1337
Github Author: Stan Chollet <stanislas.chollet@gmail.com>

Test Plan: Imported from GitHub, without a `Test Plan:` line.

Examples/UIExplorer/TabBarIOSExample.js

@@ -48,7 +48,9 @@ var TabBarExample = React.createClass({
 
   render: function() {
     return (
-      <TabBarIOS>
+      <TabBarIOS
+        tintColor="black"
+        barTintColor="#3abeff'">
         <TabBarIOS.Item
           title="Blue Tab"
           selected={this.state.selectedTab === 'blueTab'}