Update google plug-in

[sylhare]

The analytics plugin is a bit outdated, and need to be adjusted.
Also since Google + is going out, I will remove it from the options.

<!-- Global site tag (gtag.js) - Google Analytics -->
<script async src="https://www.googletagmanager.com/gtag/js?id=UA-xxxxxxx-1"></script>
<script>
  window.dataLayer = window.dataLayer || [];
  function gtag(){dataLayer.push(arguments);}
  gtag('js', new Date());

  gtag('config', 'UA-xxxxxxxx-1');
</script>

Also, if you wanne set up google analytics, don't forget to choose https if hosted on github.io

[sylhare]

All good now