title: Insert sibling item to Angular-UI-tree
body: <p>I need to insert a sibling item to tree on click in angular-ui-tree (<a href="https://github.com/angular-ui-tree/angular-ui-tree" rel="nofollow">https://github.com/angular-ui-tree/angular-ui-tree</a>)</p>
  
  <p>it means I have:</p>
  
  <pre><code>&lt;item&gt;&lt;input value"item A #1"&gt;&lt;button&gt;insert under&lt;/button&gt;&lt;/item&gt;
  &lt;item&gt;&lt;input value"item B #2"&gt;&lt;button&gt;insert under&lt;/button&gt;&lt;/item&gt;
  &lt;item&gt;&lt;input value"item C #3"&gt;&lt;button&gt;insert under&lt;/button&gt;&lt;/item&gt;
  &lt;item&gt;&lt;input value"item D #4"&gt;&lt;button&gt;insert under&lt;/button&gt;&lt;/item&gt;
  </code></pre>
  
  <p>when I click in Item C "insert under" I need to add new item between Item B and Item C - and focus this new item's input.</p>
  
  <p>How to do that?</p>
  
  <p>Thank you a lot!</p>