Update sass to version 2.12.0
Update sass to version 2.12.0

jasnow/follow-all,BryanH/follow-all,BryanH/follow-all,codeforamerica/follow-all,codeforamerica/follow-all,jasnow/follow-all,BryanH/follow-all,codeforamerica/follow-all,jasnow/follow-all