title: JQuery UI Sortable "CursorAt" not updated after changing variable
body: <p>The issue:
  Whenever I change the value on the Sortable CursorAt Left after the initiation, the new value does not update Sortable.</p>
  
  <p>Here is the Javascript function</p>
  
  <pre><code>var cursorL = 100;
  $('.s').sortable({
      helper:'clone',
      cursorAt: {left:cursorL, top:0}
  });
  $('.s').disableSelection();
  $('.me').click(function(){
      cursorL = 50;
      $('.s').sortable('refresh');
  });
  </code></pre>
  
  <p><a href="http://jsfiddle.net/kofr6f8u/" rel="nofollow">http://jsfiddle.net/kofr6f8u/</a> is the workable example. It points to the center perfectly. However, after you click the button and the cursorL value changes, the sortable will not change along with it.</p>
  
  <p>The purpose:
  I want the cursor to always point to the center of the helper or the drag element. When the window resizes, the helper or drag element will also resize itself based on the window size; thus changing the position of the CursorAt (left, right). </p>
  
  <p>Solution that I have attempted. Making the changes in Sortable('start') function. That also did not work. Adding in Sortable('refresh')</p>
  
  <p>Is there a way to update the Sortable curosrAt element after the element is changed?</p>
  
  <p>Thank you for any advice!</p>