message: Updated readme to match latest setup
diff: ```js
  import {StateNavigator} from 'navigation';
  import {NavigationHandler} from 'navigation-react';
  -import {addNavigateHandlers, Scene} from 'navigation-react-native';
  +import {NavigationStack} from 'navigation-react-native';
  var stateNavigator = new StateNavigator([
  {key: 'hello', title: 'Hello'},
  @@ -26,11 +26,10 @@ world.renderScene = ({size}) => (
  );
  stateNavigator.navigate('hello');
  -addNavigateHandlers(stateNavigator);
  -export default ({crumb}) => (
  +export default () => (
  <NavigationHandler stateNavigator={stateNavigator}>
  - <Scene crumb={crumb} />
  + <NavigationStack />
  </NavigationHandler>
  );
  ```
  