Adapt requirements

Merge pull request wp-cli#4923 from wp-cli/4921-handle-asset-less-rel…

…eases

Skip releases that lack a downloadable asset

Merge pull request wp-cli#4897 from wp-cli/bump-version-to-2-0-0

Bump version to 2.0.0

Adapt VERSION file to reflect 1.5.1 version

Merge pull request wp-cli#4656 from wp-cli/update-to-1-5-0

Update to 1.5.0

Bump version to 1.4.1

Merge pull request wp-cli#4449 from wp-cli/release-1-4-0

Bump version to 1.4.0

Merge pull request wp-cli#4273 from wp-cli/bump-1-3-0

Bump version to 1.3.0

Merge pull request wp-cli#4135 from wp-cli/bump-1-2-1

Bump version to 1.2.1

Merge pull request wp-cli#4115 from wp-cli/bump-1-2-0

Bump version to 1.2.0