title: Custom index views with ActiveAdmin
body: <p>I'm working on an application with an ActiveAdmin backend and having a hell of a time getting it to render a fairly simple custom index view.</p>
  
  <p>I have a number of 'request' records, which contain an email address and a book_id, by which they need to be grouped. I got as far as:</p>
  
  <pre><code>ActiveAdmin.register Request do
    controller do
      def index
        @requests = Requests.group(:book_id).page
      end
    end
  end
  </code></pre>
  
  <p>but this resulted in an error: ActiveSupport::OrderedHash can't be coerced into Fixnum</p>
  
  <p>I can create my own custom view in app/admin/requests/index.html.erb but then I lose the standard AA layout with the admin menu et all and can't find a good way to include it.</p>