Implementation: separate IPLD from CBOR

[nicola]

Taken from (meeting-notes/2016-09-19-ipld.md#layers)

Most of our IPLD implementations from js-ipld to js-ipfs-ipld assume that there is only one way to encode an IPLD object and this is CBOR. However, from the new CID conversations, IPLD+CBOR is what we all have implemented.

• Generalize our modules
• Create a module js-ipld-cbor(-parser|-serializer)?

note: All this is of course abstracted from the IPLD modules that by default will choose to use IPLD+CBOR

[nicola]

This effort is happening in JS-IPFS, needs to update the spec

[nicola]

This is basically been done!