title: Open Accordion only on click of the right symbol
body: <p>I would like to disable the click event that opens the accordion if I click anywhere on the heading.Instead I would like to click only on the right most symbol....
  Here it's opening if I click on the Save button..</p>
  
  <pre><code>  &lt;accordion-group is-open="status.open" template-url="accordion-group.html"&gt;
          &lt;accordion-heading&gt;
              I can have markup, too! &lt;button type="button"&gt;Save&lt;/button&gt; &lt;i class="pull-right glyphicon" ng-class="{'glyphicon-chevron-down': status.open, 'glyphicon-chevron-right': !status.open}"&gt;&lt;/i&gt;
          &lt;/accordion-heading&gt;
          This is just some content to illustrate fancy headings.
      &lt;/accordion-group&gt;
  </code></pre>
  
  <p>Here's the plunker..</p>
  
  <p><a href="http://plnkr.co/edit/vKGj5jRkhgYow6Ge7e8f?p=preview" rel="nofollow noreferrer">link</a></p>