Release v2.20.1

Release v2.20.0 (direnv#485)

Release v2.19.2 (direnv#459)

Release v2.19.1 (direnv#454)

Release v2.19.0 (direnv#441)

Release v2.18.2 (direnv#418)

Merge pull request direnv#416 from zimbatm/release-2.18.1

Release v2.18.1

Merge pull request direnv#415 from zimbatm/release-2.18.0

Release v2.18.0

Release v2.17.0

Release v2.16.0