Most of the problems with our logic were due to not having the same
logic as our exclude parameter. This refactors that out into a separate
function so we can confidently achieve that.

This adds support for rules that ignore violation codes on a per-file
basis. This takes a similar functional approach to
https://github.com/snoack/flake8-per-file-ignores which allows for glob
patterns like the `--exclude` option.

Closes #156

Instead of just using Flake8 and pylint to keep Flake8 clean, let's also
use black to make it less manual for clean-up.

Spelling and grammar fixes

See merge request pycqa/flake8!232

Refs #365

Previously we were hitting the catch-all return that decided the error
was selected. Instead, let's add specific logic since we now know how we
would hit that and we actually don't want it to be selected.

Closes #354

Also, this further highlights why naming methods is so hard. I can't
think of a better name for 'more_specific_decision_for' that isn't
wildly long and unnecessarily verbose.

Move all Violation related methods from the StyleGuide to our Violation
class.