Disable Google Analytics in development mode (#569)

layouts/partials/header.html

@@ -77,6 +77,7 @@
   <link rel="stylesheet" href="{{ "/css/" | relURL }}{{ . }}">
   {{ end }}
 
+  {{ if not .Site.IsServer }}
   {{ if .Site.GoogleAnalytics }}
     <script>
       window.ga=window.ga||function(){(ga.q=ga.q||[]).push(arguments)};ga.l=+new Date;
@@ -94,6 +95,7 @@
     <script async src="//cdnjs.cloudflare.com/ajax/libs/autotrack/{{- $sri.js.autotrack.version -}}/autotrack.js"></script>
     {{ end }}
   {{ end }}
+  {{ end }}
 
   {{ if or .Site.RSSLink .RSSLink }}
   <link rel="alternate" href="{{ .RSSLink | default .Site.RSSLink  }}" type="application/rss+xml" title="{{ .Site.Title }}">