#9 permutations and combinations

[Toby Donaldson]

Develope classes that could be useful to
students/teachers in MACM 101/202. They should
calculate factorials, combinations, etc. You should
consider using the BigInteger class.

Design, implement, test, and document classes that
support this. Create demo classes so that people can
see how to use the code. Make it as simple and as easy
to use as possible.