Scikit-optimize: Scikit-optimize version should not be hard-coded

[tritemio]

Currently scikit-optimize version is hardcoded in skopt/__init__.py. It would be better to use a system such as versioneer to automatically generate versions from tags (for releases) or from tags+commit hash for intra-releases versions. This would allow easier tracking of exact version used down to commit level improving reproducibility.

If the maintainers agree I can send a PR to add versioneer support.

[betatim]

I am +-0 on this. Is it quick to make a PR so we can see what it would look like?

[tritemio]

Done #696

[iaroslav-ai]

Thanks @tritemio !