message: Updated crumb check to use new key format
  The old key format was 3(+++) but it's now 1-3 where the first digit is a counter. So extract key by splitting on '-'.
  Back out previous change because that was just a problem because wasn't using the new key format!
diff: - (void)checkPeekability:(NSInteger)crumb
  {
  NVSceneView *scene;
  - if (crumb > 1 && self.keys.count > crumb - 1) {
  + if (crumb > 1) {
  scene = (NVSceneView *) [_scenes objectForKey:[self.keys objectAtIndex:crumb - 1]];
  }
  _navigationController.interactivePopGestureRecognizer.enabled = scene ? scene.subviews.count > 0 : YES;
  - (void)navigationController:(UINavigationController *)navigationController willShowViewController:(UIViewController *)viewController animated:(BOOL)animated
  {
  - NSInteger crumb = [((NVSceneView *) viewController.view).sceneKey intValue];
  + NSString *sceneKey = ((NVSceneView *) viewController.view).sceneKey;
  + NSInteger crumb = [[[sceneKey componentsSeparatedByString:@"-"] objectAtIndex:1] intValue];
  if (crumb < [self.keys count] - 1) {
  self.onWillNavigateBack(@{ @"crumb": @(crumb) });
  }
  