Injecting Sufia::User after Hydra::User

Given that Hydra is a dependency of Sufia the expected behavior for
the user file is:

    class User
      include Hydra::User
      include Sufia::User
    end

That way, any methods defined in Hydra::User can be overridden and
execute super in the expected order (i.e. User would lookup super in
Sufia::User and then Hydra::User)