title: After updating to Rails 5 and Devise 4.0.0.rc1, the devise authenticate_user! method is not defined
body: <p>I had a rails app which was running perfectly with devise 3 and rails 4. I updated rails to 5 and it gave <code>DEPRECATION WARNING: alias_method_chain is deprecated</code>. So i had to change the devise version to 4.0.0.rc1.</p>
  
  <p>Now it seems like the devise is not generating the methods like <code>authenticate_user!</code>, <code>is_admin</code> etc..</p>
  
  <p>I am getting the following error</p>
  
  <pre><code>Before process_action callback :authenticate_user! has not been defined (ArgumentError)
  </code></pre>
  
  <p>I tried everything including, uninstall devise and install again, then tried to create a separate model from scratch and still the methods are not defined. </p>
  
  <p>Any ideas please ?</p>