Last assignment outline.

Goal: use dictionaries, url, excel modules
More: practice with classes, use inheritance, exception handling example

Specs: menu driven program to create and update semester course listings

OO Design -----------------

CourseID - core details for a valid course ID
    - div
    - dept
    - cnum

Course - core details for one course, base class
    - number
    - title
    - credits
    - area designators (optional)
    - description (optional)
    - prereqs (optional)

CourseListing extends Course - includes semester-specific information
    - instructor
    - timeslot
    - semester
    - year

SemesterListing - collection of CourseListings
    - semester
    - year
    - courses

CoursesMain - menu driven program to manipulate course listings
    - new course
    - new semester
    - add course to semester
    - remove course from semester
    - list all courses
    - list semester courses
    - save semesters to excel file
    - load semesters from excel file
    - load courses from text file
    - save courses to text file

