Removed all.

@ndelage No rush. Thanks for any suggestions.
methods like `predict_move` whose side effect is the changing of instance variable (in this case `@best_choice`) are mysterious. If you want `best_move` to return the `@best_choice`, why can't `predict_move` return it?

In other words, if a method is going to modify internal state (instance variables) I prefer the method name to be a verb.