title: React Navigation - navigating to another tab and reset stack
body: <p>I'm trying to route from one StackNavigator to another, both of which are inside a TabNavigator. I'm currently able to get there by simply doing:</p>
  
  <pre><code>this.props.navigation.navigate('Screen3')
  </code></pre>
  
  <p>But I also want to reset that tab when I go to it. Here is how my app navigators are generally set up:</p>
  
  <pre><code>- Main (StackNavigator)
    - LoginScreen
    - MainTabs (TabNavigator)
      - Tab1 (StackNavigator)
        - Screen1
        - Screen2
      - Tab2 (StackNavigator)
        - Screen3
        - Screen4
  </code></pre>
  
  <p>How could I navigate to <code>Screen3</code> but also reset the StackNavigator <code>Tab2</code>?</p>
  
  <p>I've also tried doing this, to no avail:</p>
  
  <pre><code>let resetAction = NavigationActions.reset({
    index: 0,
    key: 'Tab2',
    actions: [
      NavigationActions.navigate({ routeName: 'Screen3' })
    ],
  });
  
  this.props.navigation.dispatch(resetAction);
  </code></pre>