message: Added can navigate back check
diff: @@ -28,7 +28,7 @@ export default ({direction, color, stateNavigator}) => {
  <TouchableHighlight
  underlayColor={color}
  onPress={() => {
  - if (url === stateNavigator.stateContext.url)
  + if (url === stateNavigator.stateContext.url && stateNavigator.canNavigateBack(1))
  stateNavigator.navigateBack(1);
  }}>
  <Text style={styles.text}>Back</Text>
  