Remove es6

[BDiehr]

This module uses const, depending on someones build process, they may or may not run node modules through a transpiler - which is why most npm modules include a built or just write it in es5 compliant javascript outright

[sindresorhus]

Duplicate of #22.

[BDiehr]

Well no point in arguing with you because it's your repo, but the vast majority of popular and maintained libraries are compiled down for you for a reason. This is only a ideological argument for enforcing people to target a higher version of node for their node_modules build process and only possibly serves to make the library more difficult to use without any maintenance benefits of ES6