title: The delete button in activeadmin does not work, and send me to the show
body: <p>The problem is that I can not delete anything from my application.
  I delete the views leaving only the public, the layout and admin.</p>
  
  <pre><code>&lt;a rel="nofollow" data-method="delete" data-confirm="Are you sure you want to delete this?" href="/admin/actividades/34"&gt;Delete Actividade&lt;/a&gt;
  </code></pre>
  
  <p>app/admin/actividades</p>
  
  <pre><code>ActiveAdmin.register Actividade do
  menu :label =&gt; "Actividades", :priority =&gt; 14
  
  form :partial =&gt; "form"
  actions :index, :show, :new, :create, :update, :edit, :destroy
  index :title =&gt; "Actividades" do 
      column "Id", :id
      column "Nome",  :name
      column "Grupo", :grupo
      column "Actividade", :category
      column "Nome da imagem",  :image_file_name
      column "Video",  :video
      column "Criado a",  :created_at
      column "Atualizada a",  :updated_at
      default_actions
  
  end
  </code></pre>
  
  <p>end</p>