Revert "* Fix of issue 550 Select2 and CSS Transforms: dropdown menu is off position: https://github.com/ivaynberg/select2/issues/550"

This reverts commit ef8c49f85f02c99bda691ae304e83f8c753a1418.

select2.js

@@ -976,7 +976,7 @@ the specific language governing permissions and limitations under the Apache Lic
 
         // abstract
         positionDropdown: function() {
-            var offset = { top: this.container[0].offsetTop, left: this.container[0].offsetLeft },
+            var offset = this.container.offset(),
                 height = this.container.outerHeight(false),
                 width = this.container.outerWidth(false),
                 dropHeight = this.dropdown.outerHeight(false),