title: Back button not working in react native navigation
body: <p>I am using react native navigation and I need to update back button design which I have achieved by following code</p>
  
  <pre><code>static navigationOptions = {
      title: '',
      headerStyle: {
        backgroundColor: '#544849',
      },
      tintColor: 'transparent',
      headerLeft: &lt;TouchableOpacity onPress={() =&gt; this.props.navigation.goBack()}&gt;&lt;Image source={require('../../img/close.png')} style={{marginTop: 10, marginLeft:10}} /&gt;&lt;/TouchableOpacity&gt;
    };
  </code></pre>
  
  <p>But this way I get error <strong>undefined is not an object(evaluating r.props.navigation)</strong></p>
  
  <p>back button does nothing without onPress.</p>