Remove dependency on incremental in favor of general compatible solution

[altendky]

#297 (review)

For get_version I think that we should have this logic

See if version is a tuple and join them with a dot.
For anything else, just call str(version_object) and strip it.

In this way it will work with incremental and any other version objects.

towncrier shouldn't care about comparing versions...

It can try to be smart and detect that you are not adding a version older than the latest one in the file... but I think that is too much...and again it should be implemented with a naive compare

So I am +1 for remove the incremental dependency :) and use simple version strings for towncrier :)

I am using a fork of towncrier in which incremental is removed as at least 3 years ago, incremental was not playing nice with private PYPI repos due to a bug in setup tools

Sounds like we could remove the dependency specifically on incremental. Give it a shot if we get a chance.