Load scripts last, add default for unknown OSes

If OS detection fails, fall back to windows and set window.os_detected
to false. In-page scripts now need to be wrapped in window.onload of
they depend on jquery or anything.
Add intro section that shows if OS detection fails
Fix image CSS for browser choice. Add nag, words

Use browser-update.org to avoid browser detection. Move some more
bootstrap classes into less
Update CSS