Return the right ActiveModel::Name on operation

Return the ActiveModel::Name for Op Model Class instead of Op Class
Add support for responder when using a model inside a namespace
delegate model_name to model_class. i hate ActiveModel and it's pseudo standard.
always delegate ::model_name to the model class and let rails sort out its weird namespacing magic.
fix the test by explicitely adding namespaces where they shouldn't be. i don't know how ActiveRecord does that and i don't wanna know it.