use dynamic versioning

[codecov[bot]]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (620958f) 95.01% compared to head (b5769d1) 95.00%.

Files	Patch %	Lines
pygam/__init__.py	66.66%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #342 +/- ## ========================================== - Coverage 95.01% 95.00% -0.01% ========================================== Files 22 22 Lines 3208 3202 -6 ========================================== - Hits 3048 3042 -6 Misses 160 160 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[dswah]

fixes https://github.com/dswah/pyGAM/issues/339