Chrome has nearly full ES6 support

[junewunder]

@jlam55555 I see you keep using function () {} for callbacks. This was necessary for previous versions of javascript, but ES6 has arrow functions, which keep the this context of the outside function. Arrow functions don't need a var thisRef = this. Also we should be using let instead of var. I say this partially to be a hipster, but also because I started by using let and let has serious benefits over var in terms of scoping. Anyway, feel free to use ES6 because people can use that on chrome by default! yay!

(anyone correct me if I'm wrong please)