Maintenance update

[artemisart]

Make pyfunctional compatible and tested on python 3.7 to 3.11 + pypy3.

This PR is a copy of #178, rebased & some deps updated to fix CI & compatibility with pypy3, closes #178.

This branch bumps some versions:

* Python ^3.6 -> ^3.7
* pytest ^2.4 -> ^7.0
* pytest-cov ^2.8.1 -> ^4.0
* covervage <5.0 -> ^5.0
* black 19.10b0 -> ^23.1

Then I ran poetry update in order to ensure that the poetry.lock file was up to date.

Using this configuration I was able to run poetry install without running in to issue #176, which makes me expect that that that should be resolved, but maybe I do not understand that well enough. It is either that, or the fact that they merged an update last week.

I could run poetry run pytest --cov=functional without issues, getting the same coverage as is currently posted on the repository. I am having issues with Travis, which is giving me trouble running the build.

The new version of black suggests small changes in the tests files, namely the removal of the u-strings and minor formatting stuff for powers. As far as I can tell this is fine. Pylint also complains about the u-strings and then some formatting which was being done in python 3.6 style (using .format as opposed to f strings). Pylint also suggests to specifying the file format when using open in the tests. I can inlcude these suggestions in the PR if you would like me to, though they are all warning level messages.

I would like to mention that there is still a travis.sh file in the project root, however as far as I can tell that is from an outdated version of Travis. Would it make sense to remove it in this in this PR?

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (e5eb3d3) 98.08% compared to head (b144963) 98.08%.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #184   +/-   ##
=======================================
  Coverage   98.08%   98.08%           
=======================================
  Files          12       12           
  Lines        2344     2345    +1     
=======================================
+ Hits         2299     2300    +1     
  Misses         45       45           

Impacted Files	Coverage Δ
functional/io.py	100.00% <100.00%> (ø)
functional/pipeline.py	98.11% <100.00%> (ø)
functional/test/test_functional.py	99.02% <100.00%> (ø)
functional/test/test_io.py	100.00% <100.00%> (ø)
functional/test/test_streams.py	93.76% <100.00%> (ø)
functional/test/test_util.py	100.00% <100.00%> (ø)
functional/transformations.py	100.00% <100.00%> (ø)

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[artemisart]

Updated dependencies for pypy compatibility, CI is green now @EntilZha