propka3 --version prints version

[speleo3]

As far as I can tell, the old --version argument and the version_label option were unused ever since this repo was set up in 2012. This patch changes the --version argument to simply print the program version and exit.

Closes #89

[codecov]

Codecov Report

Merging #113 (42c3b8a) into master (3937cb1) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #113   +/-   ##
=======================================
  Coverage   73.09%   73.09%           
=======================================
  Files          24       24           
  Lines        3958     3959    +1     
=======================================
+ Hits         2893     2894    +1     
  Misses       1065     1065           

Impacted Files	Coverage Δ
propka/lib.py	65.95% <100.00%> (+0.24%)	⬆️

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[orbeckst]

The function of --version changed. Even if it didn't work as advertised, it should be noted that functionality changed. (Under semantic versioning this would require a major new release number but I think in this case that might be overkill, especially as it was non-functional.)

Ultimately, @sobolevnrm and you should agree how you want to handle such changes. The package is also historically missing a CHANGELOG so it's hard for users to really understand what changes between versions.

I have a small concern about cyclical imports – it's not enough to block this issue, though.