cbor: encode tags prefixed to values when present.
cbor: encode tags prefixed to values when present.

We should now be able to round-trip cbor tags losslessly in a cbor<->tokenstream<->cbor decode/encoder.  This is good; but also fairly useless, because nothing but cbor supports these tags; no other serializers, nor have we yet implemented any way to alter the behavior of obj unmarshal in response to them, nor yet obj marshal to emit them.

Partially fixes #7.

Signed-off-by: Eric Myhre <2346ad27d7568ba9896f1b7da6b5991251debdf2@exultant.us>

polydawn/refmt,polydawn/go-xlate,polydawn/refmt,polydawn/go-xlate