Add priority to make less incompatible with Angular 1.2

This gets around problem introduced by angular/angular.js@31f190d but does not address the multi issue (which is well beyond my capability).

Author: mchapman

src/select2.js

@@ -12,6 +12,7 @@ angular.module('ui.select2', []).value('uiSelect2Config', {}).directive('uiSelec
   }
   return {
     require: 'ngModel',
+    priority: 1,
     compile: function (tElm, tAttrs) {
       var watch,
         repeatOption,