title: Active Admin Exporting to CSV file
body: <p>I'm using active admin to use admin functionalities in my Rails 4.0 application. I have a users table that lists </p>
  
  <ul>
  <li>id </li>
  <li>name </li>
  <li>email</li>
  <li>phone no</li>
  </ul>
  
  <p>I have also put a button on the top of the list like this.</p>
  
  <pre><code>action_item only: :index do
    link_to 'Export to CSV', '#'
  end
  </code></pre>
  
  <p>I want to export the users id name &amp; email into a csv file when I click on this button. Please help me to do this</p>