Fixed issue where foreign keys on collections without ObjectID primary keys would cause a crash
Fixed issue with criteria containing a key set to null
Fixed issue where serializeValues wasn't checking whether a string qualified as a Mongo ID before attempting to turn it into an ObjectID (this still could be done better; see @todo comment)
Fixed issue where array attributes would be over-parsed, so {'$in':["527ac6ca97649d045d000003"]} would get to line 265, and the toString() would return "527ac6ca97649d045d000003", which matches a MongoID, and bad things would happen.