title: serialize() sortable accordion
body: <p>I asked this question on the jQueryUI forums, but got no response. </p>
  
  <p>I've created a sortable accordion but I can't seem to figure out how to serialize the indexes like you can on a non-accordion sortable.  </p>
  
  <p>on my H3 elements I have the id="agendas_1234" and then the following code.  But the line where I define the params variable doesn't work.  I don't get the same [1234,3456,123] that I would get with a regular sortable (no accordion)</p>
  
  <pre><code>$(tab).find('#accordion').accordion({
      header: "&gt; div &gt; h3",
      collapsible: true
  }).sortable({
      axis: "y",
      handle: "h3",
      stop: function(event, ui) {
          stop = true;
      },
      update: function(event, ui) {
          var params = $(this).sortable('serialize');
      }
  });
  </code></pre>