Update analytics.html

_includes/analytics.html

@@ -1,17 +1,11 @@
 {% if site.g-analytics %}
-<!-- Asynchronous Google Analytics snippet -->
+<!-- Google tag (gtag.js) -->
+<script async src="https://www.googletagmanager.com/gtag/js?id={{ site.g-analytics }}"></script>
 <script>
-  var _gaq = _gaq || [];
-  var pluginUrl =
- '//www.google-analytics.com/plugins/ga/inpage_linkid.js';
-  _gaq.push(['_require', 'inpage_linkid', pluginUrl]);
-  _gaq.push(['_setAccount', '{{ site.g-analytics }}']);
-  _gaq.push(['_trackPageview']);
+  window.dataLayer = window.dataLayer || [];
+  function gtag(){dataLayer.push(arguments);}
+  gtag('js', new Date());
 
-  (function() {
-    var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
-    ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
-    var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
-  })();
+  gtag('config', '{{ site.g-analytics }}');
 </script>
 {% endif %}