Clean up CSS

[ctargett]

There are several CSS files in use, mostly coming from the theme we've borrowed, which seems to have itself borrowed CSS from Bootstrap and Font Awesome.

An analysis by the Dust-Me tool of all pages in the site shows 2,962 unused selectors across the 7 stylesheets. Many of these selectors we'll probably never use no matter what we do. Let's see what happens if we remove almost all of the unused selectors.