Update Rental_t.cpp

These be me changes. I added the getCharge test in case you want to keep it. If not, delete it.
Update Customer.cpp

Exercise 3: Took the frequentRenterPoints calculator thing and moved it to the Rental class.
Update Rental.cpp

Exercise 3: Moved the frequentRenterPoints calculator thing from the Customer class to the Rental class.
Update Rental.hpp

Exercise 3: Updated header to declare the newly moved function.
Update Customer.cpp

Exercise 4. Sort of pointless change, but it's what was asked by the prompt. getTotalCharge(it) function was created, and it simply returns it->getCharge().
Update Customer.hpp

Exercise 4: added getTotalCharge declaration.
Update Movie.cpp
Update Movie.hpp
Update Rental.cpp
Update Rental.hpp
Merge pull request #2 from EarthwormJim/master

Merge