message: Removed redundant rest from state
  Calculating it on the fly from the rest passed in from Motion. Haven't checked this works yet, but it seems right (working on native web twitter sample which doesn't have a shared element)
diff: @@ -7,14 +7,14 @@ import SharedElementRegistry from './SharedElementRegistry';
  import withStateNavigator from './withStateNavigator';
  import Freeze from './Freeze';
  import { NavigationMotionProps } from './Props';
  -type NavigationMotionState = {stateNavigator: StateNavigator, keys: string[], rest: boolean};
  +type NavigationMotionState = {stateNavigator: StateNavigator, keys: string[]};
  type SceneContext = {key: string, state: State, data: any, url: string, crumbs: Crumb[], nextState: State, nextData: any, mount: boolean};
  class NavigationMotion extends React.Component<NavigationMotionProps, NavigationMotionState> {
  private sharedElementRegistry = new SharedElementRegistry();
  constructor(props: NavigationMotionProps) {
  super(props);
  - this.state = {stateNavigator: null, keys: [], rest: false};
  + this.state = {stateNavigator: null, keys: []};
  }
  static defaultProps = {
  duration: 300,
  @@ -29,24 +29,20 @@ class NavigationMotion extends React.Component<NavigationMotionProps, Navigation
  var keys = prevKeys.slice(0, currentKeys.length).concat(newKeys);
  if (prevKeys.length === keys.length && prevState !== state)
  keys[keys.length - 1] += '+';
  - return {keys, rest: false, stateNavigator};
  + return {keys, stateNavigator};
  }
  getSharedElements() {
  var {crumbs, oldUrl} = this.props.stateNavigator.stateContext;
  - if (oldUrl !== null && !this.state.rest) {
  + if (oldUrl !== null) {
  var oldScene = oldUrl.split('crumb=').length - 1;
  return this.sharedElementRegistry.getSharedElements(crumbs.length, oldScene);
  }
  return [];
  }
  clearScene(index) {
  - this.setState(({rest: prevRest}) => {
  var scene = this.getScenes().filter(scene => scene.key === index)[0];
  if (!scene)
  this.sharedElementRegistry.unregisterSharedElement(index);
  - var rest = prevRest || (scene && scene.mount);
  - return (rest !== prevRest) ? {rest} : null;
  - });
  }
  getScenes(): SceneContext[]{
  var {stateNavigator} = this.props;
  