Revert "switch grunt-contrib-sass for grunt-sass"

This reverts commit a145f9c63580a0a0f92abef852461961a73f6287.
un-revert "switch grunt-contrib-sass for grunt-sass"

to create as a branch
moved "banner" in css to one line
switched grunt-sass back to grunt-contrib-sass

it didn’t compile properly (prism didn’t load), shame as it was so quick