Gem database_cleaner was outdated.

This caused all tests to fail. Now only a few of them fail.
Require BSON so it is available for use.

This was caught from select field test, maybe this is not the place to
require it...
Fixing has_many order_by, although test may be outdate.

Although test doesn't pass it may be outdated or biased.
http://mongoid.org/en/origin/docs/options.html
It appears that the syntax changes due to mongoid use of moped gem
instead of plain mongo gem.