Rizzi-Guestbook.php update

git-svn-id: https://plugins.svn.wordpress.org/rizzi-guestbook/trunk@983271 b8457f37-d9ea-0310-8a92-e5e31aec5664
readme.txt update

git-svn-id: https://plugins.svn.wordpress.org/rizzi-guestbook/trunk@983277 b8457f37-d9ea-0310-8a92-e5e31aec5664