Just as frontman Rivers Cuomo hinted in Spin‘s June cover story, Weezer have embarked on their “Hootenanny Tour,” a series of nationwide stops during which devout, guitar-giftedfans — chosen via YouTube tryouts — rock out live with Weezer, strumming out both band originals and covers with their garage-and-power-pop heroes. And last Friday (June 20), after stops in Phoenix and Portland earlier this