Support for ES6 import/export Syntax

[stromhalm]

Hey there,

first of all, thank you for your wonderful library!

I wanted to use it in my Svelte/Rollup based application and faced some problems with JavaScript strict mode and module import/export. As a result, I created a fork of this repo that supports ES6 modules at LogicJS-ES6. I would not recommend a merge though because that would break CommonJS compatibility. Just wanted to leave this here for everybody facing the same problem.

Keep up the good work.
@stromhalm