SASS fixes

This _should_ have no impact on the site's styling, but fixes two organizational things that were bugging me:

1. The file was SASS, not SCSS. I renamed it to .sass from .scss so the sass tools wouldn't throw errors.
2. Since SASS is compiled to CSS, we should really update the SASS and just compile it, rather than editing CSS directly. I backported a couple changes (including my own) that didn't do this. (Then I regenerated the .css)