swift234

Add flake8 config with all currently passing rules enabled.

Running flake8 prior to committing new Python code makes sure that no
regressions w.r.t. PEP 8 compliance are introduced.

Please note that all potentially controversial PEP 8 rules are disabled in this
config file. Only the remaining non-controversial and currently passing rules
are kept enabled.

Running flake8:
$ flake8

Installing flake8:
$ pip install flake8