fix(metadata): explicitly set version

[benatouba]

salem.version now correctly reflects the version of the package.

• closes #xxxx
• tests added / passed
• passes git diff upstream/master | flake8 --diff
• whatsnew entry

salem.utils reads package metadata, but version number was not explicitly set. This resulted in version numbering v0.1+githash for regardless of real release number.

[fmaussion]

Thanks! Sorry i missed this. But normally this should be done automatically based on the git tag or commit. Awaiting input from @TimoRoth on how to do this nicely - there must be a good way available somewhere.

[fmaussion]

See #250

Thanks for the report!