title: ng-model is not getting changed in ui-select
body: <p>I'm trying to achieve something very straightforward:</p>
  
  <pre><code>&lt;ui-select multiple ng-model="company.stack" theme="bootstrap"&gt;
      &lt;ui-select-match&gt;{$$item.name$}&lt;/ui-select-match&gt;
      &lt;ui-select-choices repeat="technology in technologies | filter: $select.search"&gt;
          &lt;div ng-bind-html="technology.name | highlight: $select.search"&gt;&lt;/div&gt;
      &lt;/ui-select-choices&gt;
  &lt;/ui-select&gt;
  </code></pre>
  
  <p>When changing the objects, the changes are not reflected in the model company.stack. I tried changing it to $parent.company.stack, but it still doesn't work. What am I missing?
  I'm using AngularJS v1.3.0-beta.17.</p>