How to use gulpfile.babel.js is undocumented

Created by: shadowmint

I realize this isn't a commonly used feature, but this functionality seems to have no documentation for it anywhere outside of this issue tracker.

Upgrading packages just resulted in complete breakage of my gulp workflow due to https://github.com/gulpjs/gulp/issues/1364

Please consider adding an article to https://github.com/gulpjs/gulp/tree/master/docs/recipes that documents that need for a .babelrc file, and broadly speaking, how to use es6 gulpfiles in general.