fix(sortable): enforce use of a jQuery element

Force the use of a jQuery element so even if jQuery is loaded after angular the element grabbed by jQlite becomes a jQuery element.

Closes angular-ui#93

Author: douglasduteil

src/sortable.js

@@ -12,7 +12,8 @@ angular.module('ui.sortable', [])
         return {
           require: '?ngModel',
           link: function(scope, element, attrs, ngModel) {
-
+            /* global jQuery:false */
+            element = jQuery(element);
               function combineCallbacks(first,second){
                   if( second && (typeof second === 'function') ){
                       return function(e,ui){