Merge pull request #3308 from mtarnovan/master

Yield the resource in SessionsController#new

app/controllers/devise/sessions_controller.rb

@@ -8,6 +8,7 @@ class Devise::SessionsController < DeviseController
   def new
     self.resource = resource_class.new(sign_in_params)
     clean_up_passwords(resource)
+    yield resource if block_given?
     respond_with(resource, serialize_options(resource))
   end