title: Angular ui-select placeholder not working
body: <p>We have been using ui-select (<a href="https://github.com/angular-ui/ui-select" rel="noreferrer">https://github.com/angular-ui/ui-select</a>) to theme dropdowns like select2. This functionality has largely been working apart from one aspect: default placeholders.</p>
  
  <p>The code largely follows the ui-select demos (3rd example on this page: <a href="http://plnkr.co/edit/a3KlK8dKH3wwiiksDSn2?p=preview" rel="noreferrer">http://plnkr.co/edit/a3KlK8dKH3wwiiksDSn2?p=preview</a>).</p>
  
  <p>As far as I'm concerned the default text should be that of the 'placeholder' attribute. Instead, it appears blank until you choose an option. We have been using a hack whereby we set the value of the ui-select-match, in the Angular controller to counter this issue, but this is far from perfect and clearly not how it should be used.</p>
  
  <pre><code>&lt;ui-select data-ng-model="producttype.selected" theme="select2" name="product-type"&gt;
      &lt;ui-select-match placeholder="Select a product type"&gt;
          {{$select.selected.title}}
      &lt;/ui-select-match&gt;
      &lt;ui-select-choices repeat="producttype in productTypeOptions | filter: $select.search"&gt;
          &lt;span ng-bind-html="producttype.title | highlight: $select.search"&gt;&lt;/span&gt;
      &lt;/ui-select-choices&gt;                                               
  &lt;/ui-select&gt;
  </code></pre>
  
  <p>Has anyone ecountered this problem before, or have any idea as to what we are doing wrong?</p>