v2.0.0rc0

Feat

• Add more descriptive error message for authentication
• compare .component_hash by default, support optionally strict checksum
• Make environment variables in if rules required to have a value
• store images on dockerhub

Fix

• optional dependencies always skipped when "version" undefined
• skip optional dependencies while solving dependencies
• api response string could be empty
• revert name slug re changes
• correct error message when manifest file is not a dict
• docs: fix render of '--'
• support env var in git source fields git, path
• support env var in local source fields path, override_path
• assume false when exceptions raised in if clause