Last night, the Pink Floyd tribute week on Late Night With Jimmy Fallon reached its midpoint with MGMT, like the good psych-rock students that they are, covering the Piper At The Gates Of Dawn oldie "Lucifer Sam." Visually, the band went all the way in with it: Dry ice, bubbles, rubberized yellow coveralls, a lobster, somebody playing a reel-to-reel recorder. ...