message: Initialised state with scenes
  Otherwise, pressing back on android and then going back in will call
  render without state
diff: @@ -15,6 +15,10 @@ class SceneNavigator extends React.Component<any, any> {
  return {scenes};
  });
  }
  + constructor(props, context) {
  + super(props, context);
  + this.state = {scenes: {}};
  + }
  static contextTypes = {
  stateNavigator: React.PropTypes.object
  }
  