digitalplaywright/mongoid-slug — pull request #161 by Iazel (2014-05-04 08:01:18+00:00)
Title: Mongoid4 also use Moped::BSON::ObjectId

That conditional cause a `NameError` for `Mongoid::Slug::BSON::ObjectId` on Mongoid 4.
Tested with Mongoid 4.0.0