Thanks for packaging cfv in nixpkgs!

I would change the text slightly, I hope this is fine for you.

As you probably noticed, the package is currently in unstable, but will probably be part of the next stable release in ~2 months. So right now nix-shell -p cfv on a stable NixOS install, will not work, but I don't think it makes sense go into the details in the cfv readme. Main point is that it's now in nixpkgs and I'll try to keep it there.