* Hide the docs nav on mobile, redesign it for two columns on narrow devices
* Tweak spacing on ToC
* Redesign sidebar and subnav
* Revamp subnav mobile layout so everything's on one line
* Tighten up masthead a little
* Switch the icon for the subnav and do a little icon toggling
* Fix mobile overflow since we changed guters stuff
* Add the widths
* make the subnav icon purple
