title: UI response for async onEnter - react-router
body: <p>I'm using react-router v1.0.0-rc4.</p>
  
  <p>Here is my routes:</p>
  
  <pre><code>  &lt;Router&gt;
      &lt;Route path="/" component={App}&gt;
        &lt;Route path="info" component={Info} /&gt;
        &lt;Route path="dashboard" onEnter={callAjax} component={Dashboard} /&gt;
      &lt;/Route&gt;
    &lt;/Router&gt;
  </code></pre>
  
  <p>When url change to /dashboard, onEnter will be called, an ajax request will send to server and about 1 second response time.</p>
  
  <p>So in this 1 second, UI didn't have any response. What I want to ask is anything I can do for this?</p>
  
  <p>What I'm trying to do is in dashboard component, I check the data is existed or not. If not exist, I will show spin, otherwise I will show data. But the issue is before the ajax complete, the dashboard will not be mounted.</p>
  
  <p>So please give some suggestion, thanks.</p>