add site.baseurl support

Author: Huxpro

_includes/head.html

@@ -5,7 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1">
     <meta name="description" content="{{ site.description }}">
     <meta name="keyword"  content="{{ site.keyword }}">
-    <link rel="shortcut icon" href="/img/favicon.ico">
+    <link rel="shortcut icon" href="{{ site.baseurl }}/img/favicon.ico">
 
     <title>{% if page.title %}{{ page.title }} - {{ site.SEOTitle }}{% else %}{{ site.SEOTitle }}{% endif %}</title>