title: Don't set .props.className of the React component?
body: <p>I've just updated to React 0.13.1 and am getting this warning:</p>
  
  <pre><code>Warning: Don't set .props.className of the React component. Instead, specify the correct value when initially creating the element. The element was created by ...
  </code></pre>
  
  <p>What am I doing wrong here? </p>