message: Animated on navigate instead of on back
  Needs to work when android back button pressed as well as back arrow
diff: @@ -7,6 +7,7 @@ export default class Detail extends React.Component {
  constructor(props, context) {
  super(props, context);
  const {url} = props.stateNavigator.stateContext;
  + this._onNavigate = this._onNavigate.bind(this);
  this.url = url;
  this.state = {
  contentAnimation: new Animated.Value(0),
  @@ -18,6 +19,13 @@ export default class Detail extends React.Component {
  }
  componentDidMount() {
  this._animate(false);
  + this.props.stateNavigator.onNavigate(this._onNavigate);
  + }
  + componentWillUnmount() {
  + this.props.stateNavigator.offNavigate(this._onNavigate);
  + }
  + _onNavigate() {
  + this._animate(true);
  }
  _animate(inverse) {
  Animated.timing(this.state.contentAnimation, {
  @@ -37,7 +45,6 @@ export default class Detail extends React.Component {
  const {stateNavigator} = this.props;
  if (this.url === stateNavigator.stateContext.url) {
  stateNavigator.navigateBack(1);
  - this._animate(true);
  }
  };
  render() {
  