Added helper function to fix table widths when dragging

When dragging table rows the widths of the cells compress to content and loose their set values.  I have added a helper function to the sortable options to fix the widths.

```javascript
sortable.options.helper = function(e, ui) {
  ui.children().each(function() {
     $(this).width($(this).width());
  });
  return ui;
};
```