title: maxLength attribute of numberfield in sencha touch
body: <p>I write a code something like </p>
  
  <pre><code>{
     xtype:'numberfield',
     maxLength: 3
  }
  </code></pre>
  
  <p>But max-length doesn't work for me any one have any suggestion and any alternate of <code>maxLength</code> attribute as in <code>numberfield</code> config I can see <code>maxLength</code> attribute in sencha touch docs but I don't understand why its not working in my case.</p>
  
  <p>Also it work if I write <code>textfield</code> instead of <code>numberfield</code>.</p>