Update unit testing lab for new semester.  Reformat code.  Fix a few instructions.
Minor update to reading on arrays.
Add lab on arrays, based somewhat on the old Espresso array slab.
Add sketch of lab on basic types.
Minor cleanup of I/O lab.
Revise arrays lab to make it easier to assign subproblems.
Add missing string problems to basic types lab.
Minor cleanup of unit testing lab.
Added problems on vectors to array lists.
Add note to myself to add array printing to arrays lab.
Ignore vi backups.
Add reading on references.