title: Router history with react-router 4.0.0
body: <p>In <code>react-router 4.0.0</code> the history provisoning seems to have changed, with the following <code>index.js</code></p>
  
  <pre><code>import React from 'react';
  import ReactDOM from 'react-dom';
  import { Router, Route, hashHistory } from 'react-router';
  import App from './components/App';
  import './index.css';
  
  ReactDOM.render(
    &lt;Router history={hashHistory}&gt;
      &lt;Route path="/" component={App} /&gt;
    &lt;/Router&gt;, document.getElementById('root')
  );
  </code></pre>
  
  <p>I get:</p>
  
  <pre><code>Warning: Failed prop type: The prop `history` is marked as required in `Router`, but its value is `undefined`.
  </code></pre>
  
  <p>and an error afterwards. I browsed the code but can't find any example or API how that has changed.</p>