Adding eslint to jake

How about some dogfooding? This adds eslint task to jake. I also created config file that enables node and disables no-console rule. I didn't replace jshint with eslint fully, because we actually get a bunch of errors linting our own code. Some of them seems like bugs in the rules (no-undef), and some others are valid linting errors. No ticket created for this (let me know if you need one for this).