title: How to sort multiselected items?
body: <p>I have already finished the function of grouping the selected items and unselected items, but I need to sort them in alphabetic order meanwhile.
  My js code is shown below:</p>
  
  <pre><code>$("#id").multiselect({
      beforeopen: function (event, ui) {
          var selected = $("#id option:selected");
          selected.remove();
          $("#id").prepend(selected);
          $("#id").multiselect('refresh');
      }
  });
  </code></pre>
  
  <p>How can I achieve this?</p>