title: item selected and selectable in ui-select2
body: <p>Usually, an item is removed from the list of selectable items, after being selected.<br/>
  But, when I refresh the underlying list of items, the (already) selected items, are selectable too!<br/>
  How can i avoid this?</p>
  
  <p>My view looks like this:</p>
  
  <pre><code>&lt;div ng-controller="MyCtrl" ng-init=buildList()&gt;
      &lt;button ng-click="buildList()"&gt;Refresh list&lt;/button&gt;
  
      &lt;select multiple ui-select2 data-ng-model="selectedDaltons"&gt;
          &lt;option data-ng-repeat="dalton in daltons" value="{{dalton.id}}"&gt;
              {{dalton.name}}
          &lt;/option&gt;
      &lt;/select&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>My controller:</p>
  
  <pre><code>function MyCtrl($scope) {
      // Averell is preselected (id:4)
      $scope.selectedDaltons = [4]; 
  
      // $scope.daltons is iterated in ng-repeat
      // its initially called in ng-init
      $scope.buildList = function() {
          $scope.daltons = [
              { id: 1, name: 'Joe' },
              { id: 2, name: 'William' },
              { id: 3, name: 'Jack' },
              { id: 4, name: 'Averell' },
              { id: 5, name: 'Ma' }
          ];
      };
  };
  </code></pre>
  
  <p><a href="http://jsfiddle.net/Jobacca/xnbrpe40/#base" rel="nofollow">Here it is as a jsfiddle.</a></p>