title: Devise Session Limit
body: <p>I have a Rails app running Rails 3.2.6 and Devise 2.1.2 and I want to be able to limit concurrent logins to 1.  I've tried using the Devise Security Extension but keep getting an undefined method for unique_session_id.</p>
  
  <p>Instead I want to see if I can override Devise's behavior as in this SO article: <a href="https://stackoverflow.com/questions/7068919/devise-limit-one-session-per-user-at-a-time">devise limit one session per user at a time</a></p>
  
  <p>I understand how it works and I've generated a sessions controller, but I'm not sure how to force the app to use it as an override for Devise.  Also in the controller should I be inheriting from the Application Controller or the Devise Controller?</p>
  
  <p>Everything in place right now however the app doesn't write a login_token which tells me that I'm not using the controller properly or something else might be amiss.  </p>
  
  <p>Any help is appreciated.</p>