Nobrainer, ORM for RethinkDB, support

The tests for the nobrainer.gemfile fails on Travis due to active_support not being loaded by the ORM, I think. 

Wasn't sure how to add this in with out dirtying up the tests anymore than I already have.
`if defined?(NoBrainer::Document) && records < NoBrainer::Document` would work since records is the model class.