Org-testimonies: Fixed a broken link

* org-testimonies/index.org: Fixed a broken link to John Wiegley's
day-planner instructions.

org-testimonies/index.org

@@ -13,7 +13,7 @@ Here you can add your story about using Org.
 
 * John Wiegley
 
-http://www.newartisans.com/blog_files/org.mode.day.planner.php
+[[http://newartisans.com/2007/08/using-org-mode-as-a-day-planner/][Using Org-mode as a Day Planner]]
 
 : The following document describes how to use Carsten Dominik’s excellent
 : org-mode Emacs package after the fashion of a pen-and-paper day planner.