title: Custom active admin page with index action
body: <p>I'm using rails 3, I have custom active admin page called "current_details",
  I have created controller in the admin page:</p>
  
  <pre><code>ActiveAdmin.register_page "Current Details" do
  
  controller do
  
  def index
    @milestones =  Milestone.all
    @collection =  @milestones.select{|a| a.milestone_status == false}
    @current_details = @collection.select{ |a| a.delivery_date.to_date.strftime('%m%Y') == Date.today.strftime('%m%Y') or a.delivery_date.to_date.strftime('%m%Y') &lt; Date.today.strftime('%m%Y') }          
  end
  end
  
  content only: :index do
     render 'index'
  end
  end
  </code></pre>
  
  <p>I need the index action for this, How do I get that? </p>
  
  <p>I already tried with rendering partial, It's throwing error as: Missing partial admin/current_details/index.
  I referred <a href="https://stackoverflow.com/questions/18977149/activeadmin-custom-views-which-retain-the-activeadmin-layout">this</a><br>
  Any help would be appreciable.</p>