Generalize TTT resolving #48

[imccarten1]

I didn't find any bugs, but there are a few style issues.

1. I think the method and variables k and self._k could have clearer names.
2. I don't see why GameState and Board need to be separate classes when many of their methods such as str and row and column are near duplicates of each other.
3. A different default value of k such as min(num_rows, num_columns) might make more sense. Also it would make sense to add a check that k is at most max(num_rows, num_columns).

[dmorrill10]

Thanks.

1. Yeah, I agree, but I couldn't think of a better name at the time. Maybe num_spaces_to_win?
2. I disagree. They are managing two different types of state. Board manages lower level changes to the board while GameState manages the higher level game dynamics. Also, I count 6 methods that are exact forwards but 8 that do some extra operations. I think that this separation is still conceptually useful and more readable than the alternative.
3. Right, thank you, I forgot to make that change.

[dmorrill10]

I will look at using inheritance to make GameState and Board more readable.

[dmorrill10]

@imccarten1, please review these changes and merge them or suggest additional changes.