Adding an isEqual Method

[Jud]

When TKStateMachine tries to determine if it can fire an event, it does:

[tkEventInstance.states containsObject: self.currentState];

If you haven't instantiated the current state with the exact TKState instance used when setting up the machine, this will always fail to fire events.

This fixes that issue.

[Jud]

@blakewatters Fixed that comparison. Wasn't really using my brain on that one.