title: React-navigation bar not displaying
body: <p>I am new to React-native and am trying to create scenes for my app. I am having trouble with two things: Firstly, I can't understand why the navigation bar with the title is not showing. I am using <a href="https://reactnavigation.org/" rel="nofollow noreferrer">React Navigation</a>. Secondly, I don't know whether the way I have started developing the app is correct.</p>
  
  <p><strong>Index.js</strong></p>
  
  <pre><code>import { AppRegistry } from 'react-native';
  import App from './App';
  
  AppRegistry.registerComponent('Hola', () =&gt; App);
  </code></pre>
  
  <p><strong>App.js</strong></p>
  
  <pre><code>import React, { Component } from 'react';
  import {
      View,
  } from 'react-native';
  import Hola from './src/ConversationListScreen';
  import styles from './src/styles';
  
  export default class App extends Component&lt;{}&gt; {
    render() {
      return (
          &lt;View&gt;
            &lt;Hola/&gt;
          &lt;/View&gt;
      );
    }
  }
  </code></pre>
  
  <p><strong>src/ConversationListScreen.js</strong></p>
  
  <pre><code>import React, { Component } from 'react';
  import { StackNavigator } from 'react-navigation';
  import {
      AppRegistry,
      Text,
      View,
  } from 'react-native';
  
  export default class ConversationListScreen extends Component
  {
      static navigationOptions = {
          title: 'Hola',
      };
      render() {
          return &lt;Text&gt;Hello, Navigation&lt;/Text&gt;;
      }
  }
  
  export const Hola = StackNavigator({
      ConversationList: { screen: ConversationListScreen },
  });
  
  AppRegistry.registerComponent('ConversationListScreen', () =&gt; Hola);
  </code></pre>