Relief Valve v1.1.0

Implemented enhancements:

• Improve error message if appmanifest file is invalid
• Handle changes to Steam file format slightly better
• Only show categories that have games installed #127
• Move links from code.mathphreak.me to www.matthorn.tech

Development-related changes:

• Moved from CoffeeScript to ES6/Babel
• Switched from Gulp to NPM scripts