message: Create history manager in state navigator constructor
  Easier to document than the configure call. More consistent with the mobile docs, too
diff: @@ -14,7 +14,12 @@ export default () => {
  const stateNavigator = new StateNavigator([
  {key: 'grid', route: ''},
  {key: 'detail', route: '{color}', trackCrumbTrail: true},
  - ]);
  + ], NavigationStack.HistoryManager && new NavigationStack.HistoryManager(url => {
  + const {state, data} = stateNavigator.parseLink(url);
  + return stateNavigator.fluent()
  + .navigate('grid')
  + .navigate(state.key, data).url;
  + }));
  const {grid, detail} = stateNavigator.states;
  grid.renderScene = () => <Grid colors={colors} />;
  @@ -24,18 +29,8 @@ export default () => {
  crumbs.slice(-1)[0].state === detail ? crumbs.slice(0, -1) : crumbs
  );
  - if (Platform.OS === 'web') {
  - const buildStartUrl = url => {
  - const {state, data} = stateNavigator.parseLink(url);
  - return stateNavigator.fluent()
  - .navigate('grid')
  - .navigate(state.key, data).url;
  - };
  - stateNavigator.configure(stateNavigator, new NavigationStack.HistoryManager(buildStartUrl));
  - stateNavigator.start()
  - } else {
  - stateNavigator.navigate('grid');
  - }
  + if (Platform.OS === 'web') stateNavigator.start()
  + else stateNavigator.navigate('grid');
  return stateNavigator;
  }
  