* refactor: remove Codecs table
* chore: go-cid 0.2.0
Codec table was missing dag-json and it had invalid code for dag-cbor.
It also had invalid string representation of dag-pb -- it was using
'protobuf' which is a totally different code.
This removes invalid mappings entirely.
https://github.com/multiformats/go-multicodec should be used instead.
