Raise line limit to 99 chars in linter.

A while ago pep8 introduced a controversial change that allowed for lines up to 99 characters long, instead of the traditional 79, in the case that everyone on the project could agree that they liked 99 better.

I think we can all agree on 99 (if I'm wrong, please speak  up). In this PR, I have also convinced the robots to like 99 too. This only applies to Python files.

I also moved the exclude list from the lint script and into the flake8 config file. I think it's better there, even if it looks ugly.
The configparser docs say you're right, and that as long as the second line is indented more than the first, it will be fine. However, it seems pep8/flake8 are supremely picky about the excludes format. I tried simply putting spaces after the commas, and it didn't work.

By the way, I'm defining "didn't work" as throwing lint errors in `settings.py`. I suspect flake8 (or whatever is parsing this value) isn't stripping whitespace next to commas like I would expect it to, and that when there is a newline in a configparser, it either includes the newline, the indentation spaces, a space out of nowhere, or some combination of all of those.