message: Kept state scene as false if was false
  If start on link to C with A and B as crumbs, then going back to B should keep state scene[0] as false because A still hasn't been rendered
diff: @@ -56,9 +56,9 @@ class NavigationMotion extends React.Component<NavigationMotionProps, Navigation
  var scene = this.getScenes().filter(scene => scene.key === index)[0];
  if (!scene)
  delete this.sharedElements[index];
  - var scenes = {...prevScenes, [index]: !!scene};
  + var scenes = {...prevScenes, [index]: prevScenes[index] && !!scene};
  var rest = prevRest || (scene && scene.mount);
  - return !scene || rest !== prevRest ? {scenes, rest} : null;
  + return (scenes[index] !== prevScenes[index] || rest !== prevRest) ? {scenes, rest} : null;
  });
  }
  getScenes(): SceneContext[]{
  