title: Compatible activeadmin and activeadmin_mongoid gem with rails 4.2
body: <p>How do I set up active admin with mongodb. My gem file includes following gem:</p>
  
  <pre><code>gem 'rails', '4.2.0' 
  ...
  gem 'activeadmin', github: 'activeadmin'
  gem 'inherited_resources', github: 'josevalim/inherited_resources', branch: 'rails-4-2'
  gem 'activeadmin-mongoid', github: 'elia/activeadmin-mongoid', branch: 'rails4'
  </code></pre>
  
  <p>All working fine but I am getting this error.</p>
  
  <pre><code>Showing /home/user/.rvm/gems/ruby-2.1.2@gemset/bundler/gems/activeadmin-7aef260921d4/app/views/active_admin/resource/index.html.arb where line #2 raised:
  
  undefined method `column_for_attribute' for #&lt;SuperAdmin:0x00000006a98c78&gt;
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/xrkNk.png" alt="NoMethodError in Admin::SuperAdmins#index"></p>
  
  <p>How do I fix this.</p>