Fixed mobile menu -- Tapping a non-top-level item now takes you to that page, as expected, even if the item has sub-pages.
Upgraded Compass and Susy, and needed to fix a bunch of mixin calls.
Tweaked mobile menu colors. Changed pfi_single_image block to link to medium size rather than large. Tweaked CSS enqueue to work for IE 10 and up (with help of PHP Browser Detection plugin).