* Add aasm features of ActiveRecord to Sequel! :)
* All specs pass for sequel, activerecord, and mongoid.
* Refactor Sequel models to be namespaced under “Sequel”. We
should do something similar for ActiveRecord in the specs
to avoid collisions.
Addresses #474
(cherry picked from commit df97ce754f47864abbcb837227da5c4d0ff77289)
