message: Removed redundant onAnimated calls
  The onRest handles all the onAnimated. Not calling setState if
  sharedElements drops to 0 so the Modal stays around until all shared
  elements animated
diff: @@ -34,19 +34,13 @@ class SharedElementMotion extends React.Component {
  if (this.state.url !== this.getStateNavigator().stateContext.url)
  return;
  var {onAnimating, onAnimated} = this.props;
  - var {sharedElements: prevSharedElements = [], animatedElements} = this.state;
  + var {animatedElements} = this.state;
  var sharedElements = this.context.getSharedElements();
  for(var i = 0; i < sharedElements.length && onAnimating; i++) {
  var {name, oldElement: old, mountedElement: mounted} = sharedElements[i];
  if (!animatedElements[name])
  onAnimating(name, old.ref, mounted.ref, old.data, mounted.data);
  }
  - if (sharedElements.length === 0 && prevSharedElements.length > 0) {
  - for(var i = 0; i < prevSharedElements.length && onAnimated; i++) {
  - var {name, mountedElement: mounted} = prevSharedElements[i];
  - onAnimated(name, null, mounted.ref, null, mounted.data);
  - }
  - }
  if (sharedElements.length !== 0)
  this.setState({sharedElements});
  this.animate();
  