Update release procedure
Update release procedure

It can be easy to miss something that's required for a
release, so run cargo publish as a dry run to make sure
everything's set.

carllerche/nix-rust,geofft/nix-rust,carllerche/nix-rust,geofft/nix-rust,carllerche/nix-rust,xd009642/nix,MarkusJais/nix-rust,asomers/nix,MarkusJais/nix-rust,nix-rust/nix,nix-rust/nix,geofft/nix-rust,MarkusJais/nix-rust,asomers/nix,xd009642/nix,xd009642/nix