NavigatorIOS navigationBarHidden property support

Summary:
Usage example:
```javascript
var AwesomeProject = React.createClass({
  render: function() {
    return (
      <NavigatorIOS
        style={styles.navigator}
        navigationBarHidden={true}
        initialRoute={{
          component: Example,
          title: 'Test'
        }}
      />
    );
  }
});
```
Closes https://github.com/facebook/react-native/pull/374
Github Author: Kureev Alexey <kureev-mail@ya.ru>

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

Libraries/Components/Navigation/NavigatorIOS.ios.js

@@ -50,6 +50,7 @@ var RCTNavigatorItem = createReactIOSNativeComponentClass({
     rightButtonTitle: true,
     onNavRightButtonTap: true,
     tintColor: true,
+    navigationBarHidden: true,
     backButtonTitle: true,
     titleTextColor: true,
     style: true,
@@ -235,6 +236,11 @@ var NavigatorIOS = React.createClass({
 
     }).isRequired,
 
+    /**
+     * A Boolean value that indicates whether the navigation bar is hidden
+     */
+    navigationBarHidden: PropTypes.bool,
+
     /**
      * The default wrapper style for components in the navigator.
      * A common use case is to set the backgroundColor for every page
@@ -547,6 +553,7 @@ var NavigatorIOS = React.createClass({
           backButtonTitle={route.backButtonTitle}
           rightButtonTitle={route.rightButtonTitle}
           onNavRightButtonTap={route.onRightButtonPress}
+          navigationBarHidden={this.props.navigationBarHidden}
           tintColor={this.props.tintColor}>
           <Component
             navigator={this.navigator}

React/Views/RCTNavItem.h

@@ -14,6 +14,7 @@
 @property (nonatomic, copy) NSString *title;
 @property (nonatomic, copy) NSString *rightButtonTitle;
 @property (nonatomic, copy) NSString *backButtonTitle;
+@property (nonatomic, assign) BOOL navigationBarHidden;
 @property (nonatomic, copy) UIColor *tintColor;
 @property (nonatomic, copy) UIColor *barTintColor;
 @property (nonatomic, copy) UIColor *titleTextColor;

React/Views/RCTNavItemManager.m

@@ -24,6 +24,7 @@ RCT_EXPORT_MODULE()
 RCT_EXPORT_VIEW_PROPERTY(title, NSString)
 RCT_EXPORT_VIEW_PROPERTY(rightButtonTitle, NSString);
 RCT_EXPORT_VIEW_PROPERTY(backButtonTitle, NSString);
+RCT_EXPORT_VIEW_PROPERTY(navigationBarHidden, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(tintColor, UIColor);
 RCT_EXPORT_VIEW_PROPERTY(barTintColor, UIColor);
 RCT_EXPORT_VIEW_PROPERTY(titleTextColor, UIColor);

React/Views/RCTWrapperViewController.m

@@ -65,7 +65,10 @@
   if ([self.parentViewController isKindOfClass:[UINavigationController class]])
   {
 
-    [self.navigationController setNavigationBarHidden:!_navItem animated:animated];
+    [self.navigationController
+      setNavigationBarHidden:_navItem.navigationBarHidden
+      animated:animated];
+
     if (!_navItem) {
       return;
     }