add solution to Problem 5 in Problem Set 1.

All the problems assigned in Problem Set 1 have been solved, with their
methods implemented as tests passed.

Included are the following 2 files:

	AlphabetGenerator.java
	AlphabetGeneratorTest.java

Thank you!
							Lawrence X. Amlord
							  Oct. 5th, 2014
							   Xi'an, China