Fix: Update confirmation link

Devise update had broken confirmation link and made it impossible to sign up.
More details http://stackoverflow.com/questions/18626544/devise-confirmation-token-is-invalid-when-user-signs-up
And here http://blog.plataformatec.com.br/2013/08/devise-3-1-now-with-more-secure-defaults/
It was fixed using https://github.com/plataformatec/devise/blob/2a8d0f9beeb31cd2287094c5dcf843d0bd069eb8/app/views/devise/mailer/reset_password_instructions.html.erb#L5
Fix: more coherent message upon confirmation

Devise has a new behaviour, you have to sign in after clicking the confirmation link