Inherit default ESLint recommended rules after updating to ESLint 1.0

[pdehaan]

Per http://eslint.org/docs/1.0.0/user-guide/migrating-to-1.0.0, I think we'll just need to add this to the root /index.js:

extends: 'eslint:recommended'

But from my casual testing, this will fail on anybody using eslint@0.24.1 or lower, so probably just bump the package.json version to 2.0.0 considering it's a non-backwards compat breaking change.

[pdehaan]

Fixed by #3