feat: added files to encourage PEP8

[ZlaTanskY]

PROPOSAL
To have all developers align on codestyle, Python dev's created PEP8 style guide.
Some tools to help enforce this guide are included in this PR:

• typecheck (mypy)
• docstyle (pydocstyle)
• linter (pylint)
• codestyle (pycodestyle)

By using the Makefile, it is easy to perform these checks by running the following command:
make code-qa

Similarly the unit tests can be run by running the following command:
make test-unit

Other commands can be found and/or added in the Makefile.

[ZlaTanskY]

I've not yet worked with black, but it could be a replacer for pylint if you prefer.
See https://github.com/psf/black

[sborms]

Hi @ZlaTanskY, awesome!

Could we go for black? That was also the conclusion in #54. I too heard good things about it.

[ZlaTanskY]

I have replaced pylint with black and changed the code accordingly, see 39a28fb

I also added the make command make black-check which will only check for PEP8 violations and not automatically replace them. This way you still have complete control on what would be changed. If you do like the automatic code replacement, you could always add a make command similar to the existing one and leave out the --diff flag.

EDIT: I did not add black into the current code-qa command.

[sborms]

Looks all good to me! Can you make it merge into the develop branch instead of the master? Then I'll approve it right away. The repo is structured as follows: master (released versions) > develop > issue branches. There's some info here: https://github.com/PythonPredictions/cobra/wiki/Contributing-guidelines-&-workflows.