Update the styles to match new branding

[wuz]

In an attempt to unify some theme styles and update the brand, I've put together a new website idea, which you can see here. We want to replicate something like that for the homepage and the individual pages for all the repos. The header (down to the "Dank Neon" ascii art) should be a part of every page, but the individual pages need to be updated with instructions and screenshots.