Add iOS tintColor prop to TextInput

Summary:
In response to https://github.com/facebook/react-native/issues/5595

Adds tintColor property to TextInput component for iOS:

<img width="375" alt="screen shot 2016-01-28 at 1 39 35 pm" src="https://cloud.githubusercontent.com/assets/3868826/12730689/eae58a36-c8e1-11e5-9453-70716617bfab.png">

Usage:

<img width="454" alt="screen shot 2016-01-28 at 1 42 37 pm" src="https://cloud.githubusercontent.com/assets/3868826/12730711/fedeed8e-c8e1-11e5-87d0-1621d19a0418.png">
Closes https://github.com/facebook/react-native/pull/5678

Reviewed By: svcscm

Differential Revision: D2895115

Pulled By: nicklockwood

fb-gh-sync-id: bfb52b992d5e02754fe47f409f6e8df426514718

Examples/UIExplorer/TextInputExample.ios.js

@@ -536,6 +536,25 @@ exports.examples = [
       );
     }
   },
+  {
+    title: 'Colored highlight/cursor for text input',
+    render: function() {
+      return (
+        <View>
+          <TextInput
+            style={styles.default}
+            tintColor={"green"}
+            defaultValue="Highlight me"
+          />
+          <TextInput
+            style={styles.default}
+            tintColor={"rgba(86, 76, 205, 1)"}
+            defaultValue="Highlight me"
+          />
+        </View>
+      );
+    }
+  },
   {
     title: 'Clear button mode',
     render: function () {