Added priority to directive

Fixes various problems causing the editor not to show up or not to respond to ng-model change

Closes #146
Closes #156

src/tinymce.js

@@ -13,6 +13,7 @@ angular.module('ui.tinymce', [])
 
     return {
       require: ['ngModel', '^?form'],
+      priority: 999,
       link: function(scope, element, attrs, ctrls) {
         if (!$window.tinymce) {
           return;