code: function ()
  	{
  		$.each( this.s.dt.aoColumns, function (i, column) {
  			$(column.nTh).attr('data-column-index', i);
  		} );
  	}
docs: Add a data attribute to the column headers, so we know the index of
  the row to be reordered. This allows fast detection of the index, and
  for this plug-in to work with FixedHeader which clones the nodes.
  @private