ES6 refactor

[JPeer264]

(#355 ) I did some more refactoring. Now everything except move/index, copy/ncp and remove/rimraf are as much as possible refactored to ES6. I wasn't sure on the skipped files, as they are from another library or got a comment with something like needs rewrite or similar.

[coveralls]

Coverage increased (+0.02%) to 85.138% when pulling 6eff3e5 on JPeer264:feature/refactor-es6 into 082342e on jprichardson:master.

[RyanZim]

LGTM, noticed one old comment that could be removed.

[RyanZim]

Sort of unrelated, but this comment should have been removed earlier, wouldn't hurt to remove it here.

[RyanZim]

I'm fine with doing the skipped files, all of them are already significantly modified from their original state.

If we decide to make changes in #292, you could skip ncp; not sure what we're doing there yet.

[JPeer264]

@RyanZim I am on move/index right now. As there are many functions inside I would suggest to outsource them into own files and require them separately into index.js. How you think about it?

EDIT:
This would also be a first step for a cleanup, regarding to the comment on the top of the file

[coveralls]

Coverage increased (+0.02%) to 85.138% when pulling 7471352 on JPeer264:feature/refactor-es6 into 082342e on jprichardson:master.

[RyanZim]

move/index is only 158 lines, I wouldn't split it personally, perhaps @jprichardson differs.

BTW, don't bother with copy/ncp; I'm working on that right now.

[manidlou]

@RyanZim is this ready to merge?

[RyanZim]

Merged. @JPeer264 Thanks again for all your work here.