title: extjs 4 store is undefined
body: <p>I'm creating a simple store in coffeescript but it returns as undefined when I call it in the browser console <code>Ext.getStore('visitors')</code></p>
  
  <pre><code>Ext.define 'heroico.store.Visitors',
      extend: 'Ext.data.Store'
      model: 'heroico.model.Visitor'
      storeId: 'visitors'
  </code></pre>
  
  <p>If I create it without actually extending <code>'Ext.data.Store'</code> I can find it via <code>getStore</code> method but then I can't load it in my controller in the <code>stores</code> array:</p>
  
  <pre><code>Ext.create 'Ext.data.Store',
      model: 'heroico.model.Visitor'
      storeId: 'visitors'
  </code></pre>
  
  <p>Any idea why it would behave this way?</p>