Dev: support debugging via node-inspector!

tl;dr:

// in code somewhere:
debugger

// in one terminal:
npm start

// in another terminal:
npm run debugger

Boom.
Dev: use Streamline's fibers mode.

Makes the debugging experience pretty slick: the code aligns almost 100%
line-for-line, and you can step "through" async operations (like setTimeout).

Important: you'll need to run `npm install` to get this new dependency.