replace jshint with eslint

[Melindrea]

http://eslint.org/

Since ESLint is (theoretically, at least) pluggable and has the same functionality as jshint, it feels like it'd be good to replace it. For instance, to get in a check that variable lists should be indented 4 spaces (apart from the 1st one).

var a,
    b,
    c;