Update less to 2.2.0

Fixes #15
diff --git a/templates/base.html b/templates/base.html
index 3b0bc7e..3ba7ea0 100644
--- a/templates/base.html
+++ b/templates/base.html
@@ -6,7 +6,7 @@
   <link rel="stylesheet" type="text/css" href="{{ SITEURL }}/theme/css/style.css">
   {% else %}
   <link rel="stylesheet/less" type="text/css" href="{{ SITEURL }}/theme/css/style.less">
-  <script src="//cdnjs.cloudflare.com/ajax/libs/less.js/1.6.1/less.min.js" type="text/javascript"></script>
+  <script src="//cdnjs.cloudflare.com/ajax/libs/less.js/2.2.0/less.min.js" type="text/javascript"></script>
   {% endif %}
 
   {% if FUZZY_DATES %}