title: Hide placeholder after the first entry
body: <p>I have this AngularJS code which allows user to add multiple tags.</p>
  
  <pre><code>&lt;tags-input min-length="1" add-on-comma="true" add-on-enter="true"  ng-model="modalData.tech" placeholder="Add Tags" display-property="tech"&gt;
      &lt;auto-complete source="loadAutoComplete('tech', {value:$query}) | filter : $query"&gt;&lt;/auto-complete&gt;
  &lt;/tags-input&gt;
  </code></pre>
  
  <p>I would like to hide the placeholder once the user adds at least 1 tag. How should I do this? A code example would be awesome.</p>