Move to skeleton CSS library

[preaction]

Skeleton is a minimal CSS framework without javascript and a lot smaller than bootstrap. So small we could just bundle it and be fine with it.

[preaction]

http://getskeleton.com

[preaction]

http://quirktools.com/screenfly/

Our default theme works pretty shitty on small devices. The font size is way too big.

[preaction]

Except we can't bundle non-template stuff because they don't show up as URLs. We might need to make a default "/theme" mount-point. But how does that work with multiple themes? This needs some more thought...