Edgeguides#engines.html documentation has broken codes

[ghost]

I caught an error in the codes within the Engine tutorial http://edgeguides.rubyonrails.org/engines.html that needs correcting.
Under section 4.4.1 where you override the user_class getter method inside the Blorgh module in the lib/blorgh.rb , resulting in the user_class method always returning a Class object. That will break the association declaration:

belongs_to :author, class_name: Blorgh.user_class

because Blorgh.user_class here will not be a string but a class, and hence cause a undefined method "match" error.

Even though this could be corrected by adding a to_s :

belongs_to :author, class_name: Blorgh.user_class.to_s

but I feel that would obscure the configuration setting of user_class from the application side.

[steveklabnik]

/cc @drogus @fxn