title: one bug that click event of checkbox/radiobutton in emberjs
body: <p>checkbox event:</p>
  <pre><code>&lt;input type=&quot;checkbox&quot; name=&quot;contents&quot; value=&quot;1&quot; {{action 'enable_submit'}} /&gt; 
  </code></pre>
  <p>submit button</p>
  <pre><code>&lt;button id='submit_btn' class='btn' disabled=&quot;disabled&quot;&gt;Submit&lt;/button&gt;
  </code></pre>
  <p>when user click checkbox, remove disabled of submit button</p>
  <pre><code>$(&quot;#submit_btn&quot;).removeAttr('disabled')
  </code></pre>
  <p>The result is:</p>
  <blockquote>
  <p>1, disable status of submit button can be removed normally.</p>
  <h1>2, the checkbox can't be checked again, it is the same problem on radiobutton</h1>
  </blockquote>