add provisions for incremental encode/decode

[agentm]

This looks like an interesting new serialization strategy and I am looking for a new storage backend. Could the library be used for serializing lists of X incrementally via streams or would the top-level schema interfere with that?

[fumieval]

That is not supported by the library itself because it makes sense only on top level, and the functions operates on strict ByteStrings. I think it's easy to implement it orthogonally; the winery command line tool uses a format where payloads are prefixed by their length, in decimals.