Vulcanize!

Replacing the polymerPaperCompile custom task with grunt-vulcanize
https://github.com/uProxy/uproxy/issues/686

The one part that may seem confusing is that we have to call vulcanize twice.
Once to inline everything into the HTML
then once to extract all inline JavaScript into a separate vulcanized.js

It seems to be a bug with vulcanize that it doesn't know how to deal with merging JavaScript files that are already separate from the component HTML.
Oh I'm not deleting it. It's still in src/ if you want to use it.
But I've added my own index.html one level up that uses the vulcanized.html import.
So you'll find that in Chrome and Firefox, I use the new index.html instead of popup.html