Added Don't Connect Four.

For the past few days, I've been trying to get a "Tic Tac Toe Tactics" game to work, (mostly because the name amused me!) but with only a 3x3 grid it seemed rather unfruitful and somewhat repetitive.

Instead, I bulked it up to a 6x6 grid, with a "Don't Connect Four" rule.
It seems to work ok, but I'm not sure how solvable the puzzles are. Be sure to let me know if you have too much of a hard time with them.