It used to be that Compass Minerals International (NYSE: CMP) had a very seasonal business, with its road salt products being popular only in the winter. Yet when the company brought on its plant nutrition business, it diversified Compass' exposure, and that has proven to be very helpful when winters aren't as severe as the company might hope.Coming into Wednesday's first-quarter financial report, Compass investors knew that a mild winter would hurt earnings, but they still expected strong revenue gains.