get all remaining sass files working with lib sass

to test, run:
https://gist.github.com/anonymous/bc9c74c7d2438c3f6375
from the /app/stylesheets directory
and see that it works

to re-render all sass in the app went from
294.39s user 21.77s system 273% cpu 1:55.41 total
to:
79.14s user 11.29s system 684% cpu 13.212 total

from 2 minutes down to thirteen seconds!!!

(with a bunch of stuff I can do to further optimize)

Change-Id: Ib239da39226f041d02cea4fb9d5e4f6fe3e18468
Reviewed-on: https://gerrit.instructure.com/38415
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Jeremy Stanley <jeremy@instructure.com>
Product-Review: Ryan Shaw <ryan@instructure.com>
QA-Review: Ryan Shaw <ryan@instructure.com>