title: react-router IndexRoute is not working
body: <p>I created the code below</p>
  
  <pre><code>&lt;Route path="admin" component={App} &gt;
    &lt;IndexRoute component={Product_Category} /&gt;
    &lt;Route path="product"&gt;
      &lt;Route path="category" component={Product_Category} /&gt;
      &lt;Route path="register" component={Product_Register} /&gt;
      &lt;Route path="manage" component={Product_Mgt} /&gt;
      &lt;Route path="brand" component={Product_Brand} /&gt;
    &lt;/Route&gt;
    &lt;Route path="library"&gt;
      &lt;Route path="promotion" component={Library_Promotion} /&gt;
      &lt;Route path="best" component={Library_Best} /&gt;
    &lt;/Route&gt;
  &lt;/Route&gt;
  </code></pre>
  
  <p>and I changed the code like below</p>
  
  <pre><code>&lt;Route path="/" component={App}&gt;
    &lt;Route path="admin" component={BasicSet}&gt;
      &lt;IndexRoute component={Product_Category} /&gt;
      &lt;Route path="product"&gt;
        &lt;Route path="category" component={Product_Category} /&gt;
        &lt;Route path="register" component={Product_Register} /&gt;
        &lt;Route path="manage" component={Product_Mgt} /&gt;
        &lt;Route path="brand" component={Product_Brand} /&gt;
      &lt;/Route&gt;
      &lt;Route path="library"&gt;
        &lt;Route path="promotion" component={Library_Promotion} /&gt;
        &lt;Route path="best" component={Library_Best} /&gt;
      &lt;/Route&gt;
    &lt;/Route&gt;
  &lt;/Route&gt;
  </code></pre>
  
  <p>After I changed the code, only <code>&lt;Route path="admin" component={BasicSet}</code> works. Except for that, none of pages are shown. In console, there is no error. When I remove <code>&lt;Route path="admin" component={BasicSet}</code>, all of pages are shown. I don't know why. Please solve this problem.</p>
  
  <p>Also, code below is working.</p>
  
  <pre><code>&lt;Route path="/" component={App}&gt;
    &lt;IndexRoute component={Product_Category} /&gt;
    &lt;Route path="product"&gt;
      &lt;Route path="category" component={Product_Category} /&gt;
      &lt;Route path="register" component={Product_Register} /&gt;
      &lt;Route path="manage" component={Product_Mgt} /&gt;
      &lt;Route path="brand" component={Product_Brand} /&gt;
    &lt;/Route&gt;
    &lt;Route path="library"&gt;
      &lt;Route path="promotion" component={Library_Promotion} /&gt;
      &lt;Route path="best" component={Library_Best} /&gt;
    &lt;/Route&gt;
  &lt;/Route&gt;
  </code></pre>
  
  <p>BasicSet.jsx code return only other components that works.</p>
  
  <pre><code>class BasicSet extends Component{
      render(){
          return(
            &lt;div&gt;
              &lt;Nav /&gt;
              &lt;Menu /&gt;
            &lt;/div&gt;
          );
      }
  }
  </code></pre>