cache headers for static assets (and on document GET)
tests
add feedback for errors to UI - esp. too long
fix that chrome bug where it loads the doc twice
add link to about page
expand extension map
maybe start serving highlighting on the other end to save transfer on highlight.js
start using CDNs for most assets
kick expiration back by increment on each view
Add file extensions ourselves to push state

# shared version only
some way to do announcements easily (and use for ads)
copy URL to clipboard button