title: Devise_invitable in rails 4?
body: <p>I am trying to use devise_invitable(0.1.3) in my application and my application already uses devise(3.1.0). I specified the devise_invitable in  my gem file and run bundle install it installed successfully but when i run any command it gives the following error:</p>
  
  <p>Error:
   uninitialized constant DeviseMailer (NameError)</p>
  
  <p>Can anyone tell what i am doing wrong?</p>
  
  <p>Any help would be appreciated.</p>
  
  <p>Thank You</p>