NFR: Babel support

[mattmccray]

Perhaps add a flag to transform the script with babel before executing?

It would be nice to be able to use ES6+ features:

#!/usr/bin/env nscript --babelify

export default ( shell, echo, $0 ) => {
  let msg = $0
  echo(`You say, '${ msg }', do you?`)
}

[mweststrate]

Ah that is a cool idea indeed, gonna see how feasible that is :) (or feel free to PR if you have experience with this)