Coded a git hook that runs other hooks, added a flake8 hook for
starters and prepared a hooks installation script.
Now that the multi-hook Bash script is polished, lets actually use Python.
Added imports example from: https://github.com/django/django/pull/3566.
Isort config that comes closest to the look of imports in the example,
plus changes in the example that seem necessary.
Consistent whitespaces in setup.cfg.
Added an isort pre-commit hook.

Only prints diffs with isort > 3.9.0 (develop branch).