Replace gulp-util to plugin-error and some upgrade

[Bargamut]

Hi there!

gulp-util is deprecated and replaced to plugin-error package.

See more on this page:
https://medium.com/gulpjs/gulp-util-ca3b1f9f9ac5

BTW: This request have some upgrades of devDependencies

new Buffer() // this is deprecated

Buffer.from() // some of actual variants

After replace gulp-util in test.js were some errors with code like this:

// new variant of
// stream.write(new gutil.File({
stream.write(new Vinyl({
	// some your options
	contents: es.readArray([new Buffer([0xe4, 0xf6, 0xfc, 0xdf])])
}));

and find solution (?):

var mystream = require('stream');

stream.write(new Vinyl({
	// some your options
	new mystream.Readable({objectMode: true}).wrap(es.readArray([Buffer.from([0xe4, 0xf6, 0xfc, 0xdf])]))
}));

In case of pain in your eyes - sorry about that - I just tried to help. ))

[coveralls]

Coverage increased (+0.02%) to 97.917% when pulling 07b3ea2 on Bargamut:master into 90ae4cb on heldinz:master.

[irudoy]

@heldinz when you plan to merge it?

[heldinz]

Hey @Bargamut thanks so much for this! I missed the notification somehow, so apologies for not seeing this sooner. Looks great at first glance, I will take a proper look ASAP.

[heldinz]

Thanks! 💯