Mobile layout CSS for Sugarcane

* I've added a somewhat rudimentary media query to Sugarcane that
converts the sidebar to a vertical header, using a minimum of
alterations, when viewed on a 640px-width display. Hopefully this won't
break custom CSS too much.
* Added <meta> viewport elements to Sugarcane and Jonah (and updated
Responsive's to match) to allow the media query to work on high-DPI
displays.
* Having added the above, Sugarcane's sidebar can now have
position:fixed again.
* Fixed a couple of bugs introduced in previous commits.