How can I move to using `https://cdnjs.cloudflare.com/ajax/libs/react-router/4.0.0-2/react-router.min.js` from using `https://cdnjs.cloudflare.com/ajax/libs/react-router/3.0.1/ReactRouter.min.js`?

Example using 3.x below.

HTML

```
<script src="https://unpkg.com/react@15.4.2/dist/react.min.js"></script>
<script src="https://unpkg.com/react-dom@15.4.2/dist/react-dom.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-router/3.0.1/ReactRouter.min.js"></script>

```

JS

```
let { Router, IndexRoute, Redirect, Route, Link, browserHistory } = ReactRouter;

history.replaceState(0,0,'/');

const Main = () =>
  <Router history={browserHistory}>

    <Route path='/' component={App}>
      <IndexRoute component={Home}/>
      <Route path='map' component={Map}/>
      <Route path='settings' component={Settings}/>
            <Redirect from='foo' to='/' />
      <Route path='*' component={NotFound}/>
    </Route>

  </Router>

const App = props => 
  <div>
    <Navigation>
      <Link to='/map'>Map</Link>
      <Link to='/settings'>Settings</Link>
      <Link to='/foo'>Foo</Link>
    </Navigation>

    {props.children}

  </div>

const Navigation = props => <nav {...props} />
const Home = () => <h1>Home</h1>
const Map = () => <h1>Map</h1>
const Settings = () => <h1>Settings</h1>
const NotFound = (props) => <h1>404 - Not Found</h1>

ReactDOM.render(<Main />, document.body);

```

See it in action at: <https://jsfiddle.net/developit/nvpr63eg/>

If I move to any of the CDN hosted 4.x versions though it doesn't work (unreachable code after return statement).