title: The sortable element helper is undefined using rails 4
body: <p>Heres the code:</p>
  
  <pre><code>&lt;%= javascript_include_tag :defaults %&gt;
  
  &lt;%= sortable_element("property-sort", :url =&gt; "hello") %&gt;
  </code></pre>
  
  <p>I want to implement drag-and-drop sorting in Rails. I am following the <a href="http://railscasts.com/episodes/147-sortable-lists" rel="nofollow">Railscast on sortable lists</a>. I got the error from this line <code>&lt;%= sortable_element("property-sort", :url =&gt; "hello") %&gt;</code> which tells it is undefined. </p>