store_base_sti_class_for_3_0

https://github.com/pkmiec/store_base_sti_class_for_3_0

ActiveRecord has always stored the base class in polymorphic _type columns when using STI. This can have non-trivial performance implications in certain cases. This gem adds 'store_base_sti_class' configuration options which controls whether ActiveRecord will store the base class or the actual class. Default to true for backwards compatibility.