Add support for PyLint

[davidak]

Pylint is a Python source code analyzer which looks for programming errors, helps enforcing a coding standard and sniffs for some code smells (as defined in Martin Fowler's Refactoring book).

https://pypi.org/project/pylint/

It is more popular than pyflakes (as for github stars) which flake8 (#35) uses.

[ad-si]

Thanks for the tip. We'll check it out!