log ch3ex4.py @ 48:98eb01502cf5 tip

age author description
2012-12-11 Brian Neal Completing Ch 3.3, exercise 4.2.
2012-12-11 Brian Neal Completing Ch 3.4 exercise 4.1.
2012-12-11 Brian Neal Adding author's Map.py as ch3ex4.py to represent the original version before