title: Grab host app active record objects when engine and host app have same model names
body: <p>I have a host app <code>unicorn</code> with the model <code>Article</code>.</p>
  
  <p>I also have a mountable engine hooked into the host app called <code>blorgh</code>. It also has a model: <code>Article</code>. It is namespaced, so the table name for the engine's Article is actually <code>blorgh_articles</code>.</p>
  
  <p>While inside the engine I want to grab the host app's <code>article</code>, <strong><em>not</em></strong> the engine's <code>article</code>. Is this possible?</p>
  
  <pre><code>#blorgh/app/controllers/blorgh/articles_controller.rb
  require_dependency "blorgh_application_controller"
  module Blorgh
    class ArticlesController &lt; ApplicationController
      def index
        @articles = Article.all #properly grabs all the engine's articles
        @host_app_articles = main_app.Article.all # this doesn't work. It should grab the host app's articles.
      end
      ...
    end
  end
  </code></pre>