[CLUE-Cert] Web page update.

[Dave Anselmi]

I was thinking we should add links (or perhaps the whole page) to the
Unix Review study guides mentioned here recently (201 and 202).  Then it
occured to me that the links we have may be out of date, so I'll work on
updating them.

I'll try to work on this, but the next study group would be a good time
to look at it.  I don't know if I'll make it on the 18th, so if anyone
else knows we have stale links or links we should add, let me know.

Dave