Webpack: ES6 import + const + let

[wmakley]

If you want it, this is a minimal webpack-ified version of Gloomycompanion + const and let variable safety. I fixed some more tiny bugs (and found that I made errors in my previous work). As far as I can tell, all features are working.

I marked these "minimal" changes as a branch, since I plan to do much more.

Why you would want this:

• Minified production builds (npm run build).
• Live reloading (npm run dev-server).
• ES6 imports and exports (clear dependencies, no globals).
• Modernized PWA setup with service worker.

Why you wouldn't want this: Full IE 11 support. (Edge, Chrome, Safari, and FF are fine.)

[wmakley]

Btw feel free to change the author on package.json, I never know what that should be with multiple contributors anyway.

[wmakley]

Added a rudimentary service worker implementation, which could potentially resolve #15. Not sure it's perfect though.