Add: check_wheel - Checks expiration of access to privileged group.

HOW TO USE:
===========

1. Get the current information about the user to be added to the 
   privileged group and take note of the comment (OLD_COMMENT).

       getent passwd username && finger username

2. Set the expiration date:

       sudo /usr/sbin/usermod -c "OLD_COMMENT - `date -d \ 
          'EXPIRATION_DATE' +%s`" username

   where EXPIRATION_DATE is in the following format

       DDD MMM dd HH:mm:ss PHT YYYY
       Tue Sep 22 00:00:00 PHT 2010
       x months(|weeks|days) -- see date(1) for more details

3. Verify using (1).
4. Add user to the privileged group using `usermod`.
5. When a CRITICAL alert is received:

   a. Immediately remove from the privileged group.
   b. Reset the comment to OLD_COMMENT.