Created loggedin.php

This page checks to see if the cookie user_id is set.
If it is, the user is greated with a message.
If not, the user is redirected to the index.
added security to cookie.

Added a timeout to the cookie, as well as path, host, secure, and
httponly values to the cookies.  These measures are from ch12,
script 12.5 from Ullman's book.