title: ngHide or ngShow based on number of children
body: <p>I know it is absolutely stupid thing to ask but I'm curious
  is there a way do something like:</p>
  
  <pre><code>&lt;div ng-show='this.children.length &gt; 0'&gt; // shown
     &lt;div&gt;
  
     &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>