Handle abstract_class setting in ActiveRecord.

Currently when a class that inherits from ActiveRecord::Base sets "self.abstract_class = true", that means there is not a related table for the class. It is intended to be inherited by other models that do have a related table.

https://github.com/rails/rails/blob/v3.2.13/activerecord/lib/active_record/inheritance.rb#L46

Just wrote the test (and necessary changes to other tests) and made the fix.

Craig