Modernize testing/linting configuration

[wbolster]

This simplifies and modernizes the configuration for various testing and
linting tools. Use pyproject.toml as the central location for all
configuration as much as possible.

Details:

• Move pytest config to pyproject.toml (modern location)
• Move mypy config to pyproject.toml (modern location)
• Move unit test files into already existing tests/ dir;
  use importable and recognized-by-default-by-pytest names.
• Remove seemingly unnecessary coveragerc file; it seemed mostly
  old and outdated copy/paste of boilerplate.
• Move tool config out of CI config files as much as possible (coverage
  report filenames etc) which is not only cleaner but also better for
  local development because it will use the same settings.
• make yamllint happy about all yaml/yml files

[francium]

Great work @wbolster 👍

[wbolster]

thanks, still polishing a bit, hence the draft status.

i'd like to fold in all mypy config, including excludes, into pyproject.toml but it seems i'm doing something wrong or mypy has a bug in its discovery mechanism.

[wbolster]

urgh 🙄 it turned out that

exclude = ["something.py"]

in pyproject.toml defines a list of strings, which i assumed would work.

however it seems that:

• mypy (i think) silently stringifies it into the string ["something.py"],
• then uses it as a regular expression pattern,
• this happens to be valid syntax for ‘any of the characters in between the [ and ]’
• this matched and hence excluded all discovered files
• result in an error that no files were checked

computers were a mistake hehe 🙈

[wbolster]

ok, all good it seems 👍🏼 pls have a look @francium (no rush) 🙏🏼

[codecov-commenter]

Codecov Report

Merging #65 (480eb35) into master (71afad2) will decrease coverage by 2.09%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##            master      #65      +/-   ##
===========================================
- Coverage   100.00%   97.91%   -2.09%     
===========================================
  Files            3        4       +1     
  Lines          227      239      +12     
===========================================
+ Hits           227      234       +7     
- Misses           0        5       +5     

Impacted Files	Coverage Δ
tests/test_result.py	100.00% <ø> (ø)
result/result.py	97.14% <0.00%> (-2.86%)	⬇️
setup.py	0.00% <0.00%> (ø)

[wbolster]

i think i addressed all feedback

[francium]

Just one small thing. Otherwise, great!