message: Added navigation back button
diff: @@ -15,6 +15,14 @@ var Page = () => (
  onPress={() => stateNavigator.navigate('scene')}>
  <Text>Next</Text>
  </TouchableHighlight>
  + {!!stateNavigator.stateContext.crumbs.length &&
  + <TouchableHighlight
  + style={styles.button}
  + underlayColor="#fff"
  + onPress={() => stateNavigator.navigateBack(1)}>
  + <Text>Back</Text>
  + </TouchableHighlight>
  + }
  </View>
  )}
  </NavigationContext.Consumer>
  