Merge #78

78: Update dependencies. r=vext01 a=ltratt

There are some minor code changes necessary to deal with changes in hmac.

[Note: currently nix 0.19.0 doesn't build on OpenBSD. A fix has been merged (nix-rust/nix#1318), but until a new release is made, snare's master branch won't build. Since I don't know how long that'll be, I think it's best to merge this now before it gets *too* stale, and pull in a nix fix later.]

Co-authored-by: Laurence Tratt <[email protected]>

Author: bors[bot]