title: CSSTransition Group Not Working (undefined) React.js
body: <p>I am calling in the CSS Transition Group property from React.</p>
  
  <p>In my js file: </p>
  
  <pre><code>var ReactCSSTransitionGroup = React.addons.CSSTransitionGroup;
  </code></pre>
  
  <p>I get this exact error:</p>
  
  <pre><code>Uncaught TypeError: Cannot read property 'CSSTransitionGroup' of undefined
  </code></pre>
  
  <p>Any idea?</p>