HighContrast: Update parse-sass.sh; remove Gemfile

Make parse-sass.sh use sassc instead of the old Ruby method.

gtk/theme/HighContrast/Gemfile

@@ -1,2 +0,0 @@
-source 'https://rubygems.org'
-gem "sass", "~> 3.4.0"

gtk/theme/HighContrast/parse-sass.sh

@@ -1,3 +1,13 @@
-#!/bin/sh
+#! /bin/bash
 
-bundle exec sass --update --sourcemap=none .
+if [ ! "$(which sassc 2> /dev/null)" ]; then
+   echo sassc needs to be installed to generate the css.
+   exit 1
+fi
+
+SASSC_OPT="-M -t compact"
+
+echo Generating the css...
+
+sassc $SASSC_OPT gtk-contained.scss gtk-contained.css
+sassc $SASSC_OPT gtk-contained-inverse.scss gtk-contained-inverse.css