Create TestPostOffice.java

This java program is to demonstrate multithreading.
Multithreaded Post Office Application in Java
Description	:	Every customer and post worker is a thread. Only 10 customers are allowed in the 
			store. Each customer is assigned random tasks. E.g. buy stamps, mail a letter, 
			mail a package. Time for each task is predefined. Post worker serves next customer
			in line. Service time depends on the task. Only 1 weighing scale is available. 
			The co-ordination between threads is strictly by semaphores. 
			Activities of 55 threads is demonstrated.