Upgrade to gtag.js

[ZiggyMo]

The new recommended way to track is to use gtag.js rather than analytics.js. For more details see:
https://support.google.com/analytics/answer/7538414#analyticsjs

[zhhz]

Hi ZiggyMo,

Thanks for the information. I haven't checked out gtag.js myself yet, not totally sure the requirements or pre-configuration/settings with google. So my concern here is how to not break the already existing gulp-ga users. Maybe we should add an option for switching between analyics and gtag...

Any PR will be more than welcome.

Thanks.

--Z

[xied75]

Would second this. There is no reason to worry about the breaking change, if it breaks, it might be the time for the end-user to move on, eventually they need to move with what Google supports.