Aesthetic fixes

This pull request contains some minor changes to mainly `setup.py`. Still there is a change that you might not agree with: dropping `distutils` as an alternative to `setuptools`.
I believe this improves stability since setuptools is needed anyways as it provides the `pkg_resources` module required for the `resource.package` module. In the spirit of failing as early as possible.
Don't hesitate to drop any of the changes if you see this differently.