title: Checkbox not working in header of uib-accordion
body: <p>If i place checkbox in header of uib-accordion, its not getting checked</p>
  
  <pre><code>&lt;uib-accordion&gt;
    &lt;div uib-accordion-group class="panel-default"
      is-open="daily"
      is-disabled="false"&gt;
      &lt;uib-accordion-heading&gt;
        &lt;div class="checkbox"&gt;
          &lt;label&gt;
            &lt;input type="checkbox" ng-model="daily"&gt;
            Daily
          &lt;/label&gt;
        &lt;/div&gt;
      &lt;/uib-accordion-heading&gt;
      This content is straight in the template.
    &lt;/div&gt;
  &lt;/uib-accordion&gt;
  </code></pre>