fix removal of == from AccessCode causing failing GetAccessCodeResult

This class in its current form has been corrupting my AccessCode sent on the GetAccessCodeResult request.  The ambiguous .split('=') method was removing '==' characters from my AccessCode, corrupting it and resulting in a failed request.  I've made the .split('=') method more specific by changing it to .split("?AccessCode=").  I'd be very surprised if anyone is using this class in its current form