Ma/ipv6 parse helper

Fixes to use envy's new api for address parsing. Let me know what you think of the API.

Can not be merged w/o envy changes being updated. See https://github.com/manderson26/envy/pull/7

This needs squashing, but I left it unsquashed to expose the history to review.

@marcparadise @seth @hosh @sdelano @oferrigni