Update versioneer to 0.21

[aragilar]

Rebased version of #36.

[pep8speaks]

Hello @aragilar! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file src/pytest_mpi/_version.py:

Line 342:80: E501 line too long (84 > 79 characters)
Line 432:80: E501 line too long (80 > 79 characters)
Line 435:80: E501 line too long (82 > 79 characters)

• In the file versioneer.py:

Line 194:80: E501 line too long (87 > 79 characters)
Line 196:80: E501 line too long (86 > 79 characters)
Line 224:80: E501 line too long (85 > 79 characters)
Line 255:80: E501 line too long (87 > 79 characters)
Line 257:80: E501 line too long (83 > 79 characters)
Line 259:80: E501 line too long (86 > 79 characters)
Line 664:80: E501 line too long (81 > 79 characters)
Line 758:80: E501 line too long (85 > 79 characters)
Line 848:80: E501 line too long (80 > 79 characters)
Line 851:80: E501 line too long (85 > 79 characters)
Line 1276:80: E501 line too long (84 > 79 characters)
Line 1473:80: E501 line too long (80 > 79 characters)
Line 1476:80: E501 line too long (82 > 79 characters)
Line 1746:80: E501 line too long (83 > 79 characters)

[codecov]

Codecov Report

Merging #38 (b4c6b6b) into master (daa00f6) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #38      +/-   ##
==========================================
- Coverage   99.19%   99.18%   -0.01%     
==========================================
  Files           3        3              
  Lines         124      123       -1     
==========================================
- Hits          123      122       -1     
  Misses          1        1              

Impacted Files	Coverage Δ
src/pytest_mpi/__init__.py	99.09% <100.00%> (-0.01%)	⬇️
src/pytest_mpi/_version.py	100.00% <100.00%> (ø)

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[aragilar]

bors r+

[bors]

Build succeeded:

• aragilar.pytest-mpi
• codecov/patch
• codecov/project