Add local config to disable disqus and analytics

_includes/disqus.html

@@ -1,3 +1,4 @@
+{% if site.enable_disqus %}
 <div id="disqus_thread"></div>
 <script type="text/javascript">
     /* * * CONFIGURATION VARIABLES * * */
@@ -11,3 +12,4 @@
     })();
 </script>
 <noscript>Please enable JavaScript to view the <a href="https://disqus.com/?ref_noscript" rel="nofollow">comments powered by Disqus.</a></noscript>
+{% endif %}