stackage2nix-0.4.0: CHANGELOG.md

# 0.3.0

- Initial Hackage release
- Add CHANGELOG.md

# 0.4.0
- Add `--resolver` option to generate full stackage packages set
- Add Nix wrapper, see `nix/README.md`
- Upd support cabal2nix >2.5
- Fix honor `--hackage-db` flag