Gulpfile changes

[jamiebuilds]

• Uses gulpfile.babel.js
• Bumps gulp
• Starts to use ES6

Finally I also started moving all the contents of tasks into functions. There's more refactoring work to do here, but you'll notice that there's a bunch of extra tasks that people create when writing gulp when you can actually just use normal functions. I started the work of moving things over like this:

function clean(dir, cb) {
  del([dir], cb);
}

gulp.task('clean', done => clean(destinationFolder, done));
gulp.task('clean-tmp', done => clean('tmp', done));

Again, more refactoring can be done here, but for now everything lives within separate functions than their tasks.

[jamiebuilds]

Hmm, for some reason istanbul is getting all upset

[jamiebuilds]

Opened an issue in Babel

[jamesplease]

Sry, updated the Gulpfile this morning @thejameskyle 🙊

[jamesplease]

@thejameskyle want to split this out into smaller, easier-to-merge PRs? This is good stuff.

[jamesplease]

ping @thejameskyle

[jamesplease]

Opened two issues for the changes here: #211 and #212