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.

React/Views/RCTTabBar.h

@@ -13,6 +13,9 @@
 
 @interface RCTTabBar : UIView
 
+@property (nonatomic, strong) UIColor *tintColor;
+@property (nonatomic, strong) UIColor *barTintColor;
+
 - (instancetype)initWithEventDispatcher:(RCTEventDispatcher *)eventDispatcher NS_DESIGNATED_INITIALIZER;
 
 @end

React/Views/RCTTabBar.m

@@ -114,6 +114,16 @@
   }];
 }
 
+- (void)setBarTintColor:(UIColor *)barTintColor
+{
+  _tabController.tabBar.barTintColor = barTintColor;
+}
+
+- (void)setTintColor:(UIColor *)tintColor
+{
+  _tabController.tabBar.tintColor = tintColor;
+}
+
 #pragma mark - UITabBarControllerDelegate
 
 - (BOOL)tabBarController:(UITabBarController *)tabBarController shouldSelectViewController:(UIViewController *)viewController

React/Views/RCTTabBarManager.m

@@ -23,4 +23,7 @@ RCT_EXPORT_MODULE()
   return [[RCTTabBar alloc] initWithEventDispatcher:_bridge.eventDispatcher];
 }
 
+RCT_EXPORT_VIEW_PROPERTY(tintColor, UIColor)
+RCT_EXPORT_VIEW_PROPERTY(barTintColor, UIColor)
+
 @end