utils.cid should uses the serialized dag node

[wanderer]

can utils.cid take in the serialized dag node instead of the node it self?

Proposal

util.cid(serializedNode, callback)

get the CID of the serialized dagNode

callback must have the signature function (err, cid), where err is an Error is the function fails and cid is a CID instance of the dagNode.

Rational

Currently resolver.put need to serialize the data twice (here and here). This causes preformance overhead can lead to rather confusing bugs.

[daviddias]

Added to spec update proposal. Let's follow up on the discussion there -> #11 (comment)