Used Google's new Tag Manager code (hexojs#110)

Author: DibranMulder

layout/_partial/google-analytics.ejs

@@ -1,14 +1,12 @@
 <% if (theme.google_analytics){ %>
-<!-- Google Analytics -->
-<script type="text/javascript">
-(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
-(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
-m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
-})(window,document,'script','//www.google-analytics.com/analytics.js','ga');
-
-ga('create', '<%= theme.google_analytics %>', 'auto');
-ga('send', 'pageview');
+<!-- Global site tag (gtag.js) - Google Analytics -->
+<script async src="https://www.googletagmanager.com/gtag/js?id=<%= theme.google_analytics %>"></script>
+<script>
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
 
+  gtag('config', '<%= theme.google_analytics %>');
 </script>
 <!-- End Google Analytics -->
-<% } %>
+<% } %>