update Sass to latest 3.1.18
update Sass to latest 3.1.18

alademann/bootstrap,liferay/alloy-bootstrap,smt/sass-twitter-bootstrap,alademann/bootstrap,liferay/alloy-bootstrap,liferay/alloy-bootstrap,jlong/sass-bootstrap-defunct,smt/sass-twitter-bootstrap,pure-zero/sass-twitter-bootstrap,jlong/sass-bootstrap-defunct,pure-zero/sass-twitter-bootstrap,thanj/quilt-next,thanj/quilt-next,alademann/bootstrap,pure-zero/sass-twitter-bootstrap