Grant Gustin confirmed today on Twitter that season three of “The Flash” will be dealing with the greatest Flash story ever told (in this writer’s opinion). Flashpoint! FLASHPOINT. This is not drill. https://t.co/nzq2NJh9pl — Grant Gustin (@grantgust) June 20, 2016 Penned by Geoff Johns, the story sees an alternate timeline where Barry is no longer…