Release 20180201

Release 20180201

Merge with NicoHood's Arc fork

• General cleanup of outdated gtk versions and extras
• Readme update
• Minor fixes for cinnamon and xfce4
• Add budgie desktop styling arc-design/arc-theme#17
• Slightly darken fonts for light theme to improve contrast arc-design/arc-theme#15
• Switch building from gulp to sassc
• Mate screensaver styling arc-design/arc-theme#27
• Install plank theme with makefile directly