title: Issue getting list to collapse with nestedSortable
body: <p>I can't seem to get the collapsible part working with <a href="http://mjsarfatti.com/sandbox/nestedSortable/" rel="nofollow">nestedSortable</a>. </p>
  
  <p><a href="http://jsfiddle.net/meisam/vq9dD/" rel="nofollow">http://jsfiddle.net/meisam/vq9dD/</a></p>
  
  <p>Here is the javascript I'm using:</p>
  
  <pre><code>$('ol.sortable').nestedSortable({
      disableNesting: 'no-nest',
      forcePlaceholderSize: true,
      handle: 'div',
      helper: 'clone',
      items: 'li',
      opacity: .6,
      placeholder: 'placeholder',
      revert: 250,
      tabSize: 25,
      tolerance: 'pointer',
      toleranceElement: '&gt; div',
      isTree: true,
      startCollapsed: true,
      update: function () {
          order = $('ol.sortable').nestedSortable('serialize');
          console.log(order); 
      }
  });
  
  $('.disclose').on('click', function() {
      $(this).closest('li').toggleClass('mjs-nestedSortable-collapsed').toggleClass('mjs-nestedSortable-expanded');
  })
  </code></pre>