perform fix for angular-ui#974

Originally from homerjam@637be08

Author: pgrm

src/uiSelectSortDirective.js

@@ -93,6 +93,8 @@ uis.directive('uiSelectSort', ['$timeout', 'uiSelectConfig', 'uiSelectMinErr', f
 
         move.apply(theList, [droppedItemIndex, newIndex]);
 
+        scope.$parent.$selectMultiple.updateModel();
+
         scope.$apply(function() {
           scope.$emit('uiSelectSort:change', {
             array: theList,