Ability to set params to authentication helpers

[entity1991]

In file https://github.com/spree/spree_auth_devise/blob/master/lib/spree/authentication_helpers.rb need to provide ability to set params to the links for custom needings.

F.E.: spree_signup_path(layout: 'home')- not working (expected 0 args), but this is working: spree.signup_path(layout: 'home')