Provisional Rails 4 updates; specs pass

 - Mongoid 4 uses upstream bson lib enforcing serialization with $oid;
   we unwrap by monkey-patching like promiscous ( http://git.io/cDladA )
 - Rspec 3 deprecations quieted
It is used below though. Apparently Mongoid 3 is more forgiving about undefined fields?

(squashes an error under rails 4)