Empty Response on Parse Error in json2 Server

[dustinfox-code]

V2/JSON2 Server
When a payload has invalid JSON in the body of the request to the RPC Server, the server fails silently and returns an empty payload with 200 status code as a response.

This error should be captured and returned as a JSON2 error for Invalid Request.

There is already a PR that is addressing this issue: #61
It would help to have this reviewed and merged.

[colega]

@dustincfox just a ping on this since my PR was already merged and released 👍