Proposal: Switch ESLinting to Airbnb's

[cmc333333]

Airbnb's linter configuration has become a decent standard; let's adopt it rather than rolling out own. I propose we include eslint-config-airbnb and replace our existing eslint with

extends: airbnb

This will no doubt raise lots of issues; we can go through them and turn off all of those rules to a "quiet" state and then begin fixing.

[cmc333333]

Done and done!