title: Traceur runtime: Super expression must either be null or a function, not undefined
body: <p>Learning ES6 and have run in to the following error straight off <code>Super expression must either be null or a function, not undefined.</code> Really unsure where my problem is, if anyone could help that would be great.</p>
  
  <p><strong>main.js</strong></p>
  
  <pre><code>'use strict'
  
  import Backbone from 'exoskeleton';
  import App from './views/App';
  
  
  var onDOMReady = () =&gt; {
      console.log('inside dom ready');
      window.app = new App();
  }
  
  if(document.readyState === 'complete' || document.readyState === 'interactive' || document.readyState === 'loaded' ) {
      onDOMReady();
  } else {
      document.addEventListener('DOMContentLoaded', onDOMReady);
  }
  </code></pre>
  
  <p><strong>App.js</strong></p>
  
  <pre><code>'use strict'
  
  import Backbone from 'exoskeleton';
  
  class App extends Backbone.View {
  
      initialize () {
          console.log('App: Init');
      }
  
      render () {
          console.log('App: Render');
      }
  
  }
  
  export default App;
  </code></pre>