Add LightBox to example app on Android (#982)

example/src/screens/FirstTabScreen.js

           <Text style={styles.button}>Show Modal Screen</Text>
         </TouchableOpacity>
 
-        {
-          Platform.OS === 'ios' ?
-            <TouchableOpacity onPress={ this.onLightBoxPress.bind(this) }>
-              <Text style={styles.button}>Show LightBox</Text>
-            </TouchableOpacity> : false
-        }
+        <TouchableOpacity onPress={ this.onLightBoxPress.bind(this) }>
+          <Text style={styles.button}>Show LightBox</Text>
+        </TouchableOpacity>
 
         {
           Platform.OS === 'ios' ?

example/src/screens/LightBoxScreen.js

   }
 }
 
-var styles = StyleSheet.create({
+const styles = StyleSheet.create({
   container: {
-    flex: 1,
     width: Dimensions.get('window').width * 0.8,
     justifyContent: 'center',
     alignItems: 'center',

example/src/screens/index.android.js

 import ModalScreen from './ModalScreen';
 import CollapsingTopBarScreen from './CollapsingTopBarScreen';
 import InAppNotification from './InAppNotification';
+import LightBoxScreen from './LightBoxScreen';
 
 // register all screens of the app (including internal ones)
 export function registerScreens() {
   Navigation.registerComponent('example.SideMenu', () => SideMenu);
   Navigation.registerComponent('example.CollapsingTopBarScreen', () => CollapsingTopBarScreen);
   Navigation.registerComponent('example.InAppNotification', () => InAppNotification);
+  Navigation.registerComponent('example.LightBoxScreen', () => LightBoxScreen);
 }