[Cs3] grades for labs 5 and 6 are in

[Mikhail Nesterenko]

in general. For the student roster labs, the code simplifies if the
storage is a vector of pairs (or similar construct): with the first
being a student name and the second - a vector of classes this student
is enrolled in.

For the airline booking class, associative containers (that enforce
key uniqueness) simplify code.

Thanks,
-- 
Mikhail