title: Prevent user from returning to previous screen StackNavigator
body: <p>I want to do a simple task: after a successful login redirect the user to his home page. I use react-navigation's <code>StackNavigator</code> for that purpose:</p>
  
  <pre><code>// App.js
  
  class App extends Component {
    render() {
      return (&lt;RootStack /&gt;);
    }
  }
  
  const RootStack = createStackNavigator(
    {
      Login: { screen: Login, navigationOptions: { header: null }},
      Home: { screen: Home, navigationOptions: { header: null }}
    },
    {
      initialRouteName: 'Root'
    }
  )
  </code></pre>
  
  <p>How do I prevent user from returning to Login screen after login? To prevent use back button in android, I would use this one:</p>
  
  <pre><code>// Home.js
  
  import React, { Component} from 'react';
  import { ... , BackHandler } from 'react-native';
  
  class Home extends Component {
      constructor(props) {
          super(props);
          BackHandler.addEventListener('hardwareBackPress', this.onBackButtonPressAndroid);
      }
      onBackButtonPressAndroid = () =&gt; {
          return true;
      }
  }
  </code></pre>
  
  <p>But doing this way, I disable back button at all. Is there another way to achieve the goal?</p>