[CSI] optional labs opened

[Mikhail Nesterenko]

CSI students,

I opened two extra labs in the lab site. They deal with vectors and
multidimensional arrays. Both topics are on the exams so you are
encouraged to practice them. 

The two labs will _not_ be graded unless you ask your TA to grade
them. No extra credit will be assigned for completion of these
labs. The labs are optional so doing them is not required.

Thanks,
-- 
Mikhail