Update TicTacToeApp

added a check before setToken is called to ensure the value entered by the user is valid (i.e.: not above 2 and not in a place x,y that already has a value X or O). 

I think changing the value from 0,1,2 to 1,2,3 will be more user friendly; add that in future update. 
I want to look at creating a drawn board instead of one that uses a formatted array next.