add solution to Part 2 of OOP Java in Lab 0.2.

Modified is the following file:

	oop_answer.md

Besides, the following 2 files are newly added:

	src/lights/ColoredLight.java
	src/lights/ColoredLightTest.java

Thank you!
							Lawrence X. Amlord
							  Apr 29th, 2014
							  Xi'an, China