Adds static final variables to TicTacToe.java

Adds ZERO, ONE, TWO, and THREE as static final variables and allows
removal of hard coded numbers within the actual code.
Dr Garrett updated this file via email

Dr. Garrett sent a file revision via email.
Renames Test Cases - Adds full testing

Renames Test Cases to
TopRow-MiddleRow-BottomRow-LeftColumn-CenterColumn-RightColumn-DiagonallyAsX-DiagonallyAsO
and raises testing coverage to 100 percent.