13-year-old Reece Harding has both hands full dealing with one headstrong mare who's all go and no whoa.    When a wildfire threatens their corner of Colorado, it's going to take all of Reece's mad horse skills and some Appaloosa luck to save the day and prove to herself-and her family-she can handle Kip, the horse who carries the stars on her rump and a fire in her heart.