title: How to authenticate using warden.authenticate!
body: <p>I would like to do a 'sign-in or register' on the fly when posting a comment to my forum.  I am using Devise/Warden.</p>
  
  <p>I want to do something like this:</p>
  
  <pre><code>user = warden.authenticate!(params[:email], params[:password])
  sign_in(:user, user)
  </code></pre>
  
  <p>Can anyone give me some tips on how to do this?</p>
  
  <p>Thanks!</p>