Filterable redirect code

git-svn-id: http://yourls.googlecode.com/svn/trunk@884 12232710-3e20-11de-b438-597f59cd7555
Wrong shortlink. Bleh.

git-svn-id: http://yourls.googlecode.com/svn/trunk@885 12232710-3e20-11de-b438-597f59cd7555