Add specific support for version implementations

[Julian]

It feels like there may be what to do specifically with e.g. incremental.Version, packaging.Version, semver.Version, and the 8000 other version implementations.

Maybe we only care about some of them, especially since "do something" potentially just means "know how to convert them back to strings", but adding this at least to investigate.

[adiroiban]

I hope we can continue to use regret with just text strings :)

I guess that more specific version implementation (other than string) is required for comparing versions.

If we need to print the version the message just str(version)

[Julian]

Is "have" there meant to be "hope"? My thought was yeah definitely it should always be possible to keep using text strings, but that if you had a more sophisticated object, as you said, for comparisons perhaps, that that'd be the reason to support something else.

But yeah comments definitely welcome if you have ideas.