Add authenticity token to return parameters

Devise is not storing the authenticated user in the session anymore if CSRF token validation fails.
https://github.com/plataformatec/devise/blob/master/lib/devise/strategies/base.rb#L5

I had to face this issue after recognizing, that (even after a successful authentication through the OpenID provider) the user was not kept logged in. I fixed the problem by sending the authenticity token with the return parameters.