Overhaul: ES6, ESLint, package.json, some smaller fixes

[flying-sheep]

Supersedes #11.

I used a simpler UMD-style function without AMD, because browserify/webpack don’t need that, and ESLint only works with a IIFE.

all commits are rather small, except for the ESLint style thing, so just look at them individually, please.

I also fixed a bug that occurs if e.g. $.fn.dataTable doesn’t exist (only DataTable with “D”)

[ashl1]

Whoaaa!
I'm planed to move to ES6 in month, but you 'very already done it. Great job!
I'll look at next week