title: ActiveAdmin batch email
body: <p>I started  using active admin for a little Rails 4.2.0 app for the administrative backend, and I am trying to send batch emails. I can not find in the documentation how to do so( Maybe I am looking in the wrong places). I have already a mailer working on the "non-admin" views using Mandrill. The app is already deployed in Heroku and all works. </p>
  
  <p>I am using on my Gemfile</p>
  
  <pre><code>gem 'activeadmin', github: 'activeadmin'
  </code></pre>
  
  <p>My admin/user.rb looks like this:</p>
  
  <pre><code>ActiveAdmin.register User do
    permit_params :email
                  :encrypted_password
                  :reset_password_token
                  :reset_password_sent_at
                  :remember_created_at
                  :sign_in_count
                  :current_sign_in_at
                  :last_sign_in_at
                  :current_sign_in_ip
                  :last_sign_in_ip
                  :created_at
                  :updated_at
                  :username
                  :first_name
                  :last_name
  </code></pre>
  
  <p>And I have also a very simple ContactController that has the actions new_contact and create_contact in order to send the emails out.</p>
  
  <p>I also posted this question on ActiveAdmin Google Groups.</p>
  
  <p>Any ideas on how to implement batch emails from ActiveAdmin?
  Can this be done? </p>