The exploits of Jack Kerouac and Neal Cassady were first described in “On the Road,” Kerouac’s autobiographical novel featuring alter-egos Sal Paradise and Dean Moriarty, more than a half-century ago. But the stars of the book’s first-ever film adaptation say they believe the Beat bible resonates as much as ever, and that it has coursed through their lives in unexpected ways. “I read it at 14 or…