Try to decode JSON the request.
Merge pull request #193 from Gizra/decode-request

Try to decode JSON the request
Issue #194: Discovery for fields by @e0ipso, @nader77 and @amitaibu.
Issue #201: Refactor version negotiation.
Fix handling of 404.
Discovery endpoint by @amitaibu and @e0ipso.
Self url should point to the RESTful URL.
Document the discovery options.