add subtitle support to navigation bar

example/src/app.js

     navigatorStyle: {
       navBarBackgroundColor: '#4dbce9',
       navBarTextColor: '#ffff00',
+      navBarSubtitleTextColor: '#ff0000',
       navBarButtonColor: '#ffffff',
       statusBarTextColorScheme: 'light'
     }

example/src/screens/StyledScreen.js

           <TouchableOpacity onPress={ this.onPopPress.bind(this) }>
             <Text style={styles.button}>Pop Screen</Text>
           </TouchableOpacity>
+  
+          <TouchableOpacity onPress={ this.onSetSubtitlePress.bind(this) }>
+            <Text style={styles.button}>Set Subtitle</Text>
+          </TouchableOpacity>
+  
+          <TouchableOpacity onPress={ this.onSetTitleImagePress.bind(this) }>
+            <Text style={styles.button}>Set Title Image</Text>
+          </TouchableOpacity>
 
         </View>
 
   onPopPress() {
     this.props.navigator.pop();
   }
+  
+  onSetSubtitlePress() {
+    this.props.navigator.setTitle({
+      title: 'title',
+      subtitle: 'subtitle',
+      navigatorStyle: {
+        navBarSubtitleTextColor: '#ff00ff',
+        navBarTextColor: '#ffff00'
+        
+      }
+    })
+  }
+  
+  onSetTitleImagePress() {
+    this.props.navigator.setTitle({
+      title: 'title',
+      titleImage: require('../../img/one.png'),
+    })
+  }
+  
 }
 
 const styles = StyleSheet.create({

src/deprecated/platformSpecificDeprecated.ios.js

         <NavigationControllerIOS
           id={navigatorID}
           title={screen.title}
+          subtitle={params.subtitle}
           titleImage={screen.titleImage}
           component={screen.screen}
           passProps={{
 
   Controllers.NavigationControllerIOS(navigator.navigatorID).push({
     title: params.title,
+    subtitle:params.subtitle,
     titleImage: params.titleImage,
     component: params.screen,
     animated: params.animated,
 
   Controllers.NavigationControllerIOS(navigator.navigatorID).resetTo({
     title: params.title,
+    subtitle: params.subtitle,
     titleImage: params.titleImage,
     component: params.screen,
     animated: params.animated,
 
 function navigatorSetTitle(navigator, params) {
   Controllers.NavigationControllerIOS(navigator.navigatorID).setTitle({
-    title: params.title
+    title: params.title,
+    subtitle: params.subtitle,
+    titleImage: params.titleImage,
+    style: params.navigatorStyle
   });
 }
 
         <NavigationControllerIOS
           id={navigatorID}
           title={params.title}
+          subtitle={params.title}
           titleImage={params.titleImage}
           component={params.screen}
           passProps={passProps}