Dave Mason, the guitarist who wrote the classic rock standard “Feelin’ Alright?” while he was a member of Traffic and later found solo success with the propulsive “Only You Know and I Know” and the soft-rock staple “We Just Disagree,” died on Sunday. He was 79. A cause of death was not immediately available. “On behalf of his family, it is with deep and profound sadness that we share the news of the passing of Dave Mason,” a statement read. “Dave Mason lived a remarkable life devoted to the