message: Compared state and props navEvent
  Only update if current scene is the same as comparing navigationEvents because only update state navigationEvent when it's the current scene
diff: @@ -14,10 +14,8 @@ class Scene extends React.Component {
  var {state, crumbs} = navigationEvent.stateNavigator.stateContext;
  return (state && crumbs.length === crumb) ? {navigationEvent} : null;
  }
  - shouldComponentUpdate(props) {
  - var {crumb, navigationEvent} = props;
  - var {state, crumbs} = navigationEvent.stateNavigator.stateContext;
  - return state && crumbs.length === crumb;
  + shouldComponentUpdate(props, state) {
  + return state.navigationEvent === props.navigationEvent;
  }
  render() {
  var {navigationEvent} = this.state;
  