title: Skip authentication for specific member action in ActiveAdmin
body: <p>I'm trying to skip the authentication for a custom ActiveAdmin member action that I've created. Here's what I've been trying, but it still brings me to the login page.</p>
  
  <pre><code>ActiveAdmin.register Foo, as: "Foos" do
  
    controller do
      skip_before_action :authenticate_admin_user!, only: :bar
    end
  
    member_action :bar, method: :get do
      # render something
    end
  
  end
  </code></pre>
  
  <p>Versions:</p>
  
  <ul>
  <li>Rails: 4.1.1</li>
  <li>ActiveAdmin: 1.0.0.pre1</li>
  </ul>