layout: show the year of now in the top page with Liquid Extensions

FYI: https://github.com/mojombo/jekyll/wiki/Liquid-Extensions

Author: Haruka Yoshihara

_layouts/en.html

@@ -23,7 +23,7 @@
       <hr>
 
       <footer>
-        <p>Copyright &copy; 2012 The ruby-gettext project</p>
+        <p>Copyright &copy; 2012-{{ site.time | date:"%Y" }} The ruby-gettext project</p>
         <p>Copyright &copy; 2003-2006 Masao Mutoh</p>
         <p>
           This document is distributed under the terms of the