A world of model planes, trains and automobiles, as well as numerous games and other items, soon will be leaving Cumming. Hobby Town USA, which has been one of Forsyth County’s few hobby shops for the past decade, is in the midst of a going-out-of-business sale. Owner Steve Emerson, a hobbyist since he started flying model airplanes at age 10, said the business is a victim of growing online consumerism.