Play JSON support

[gmethvin]

It'd be nice to be able to easily use my play-json serializers with this library. That would make it really easy to use the same JSON representation in RethinkDB that I use elsewhere in my Play application. Using Jackson directly is not particularly nice in Scala, and it doesn't provide any nice ways of validating the serializers at compile time.

Ideally you wouldn't need to tie things to a specific JSON implementation. It might be better to use type classes for your serializers and have a separate module for play/play-json support, like the play-reactivemongo module provides for reactivemongo.

[anand-singh]

+1