By: Addison Wylie Jay and Mark Duplass hopped on board Sean Baker’s Tangerine to lend their support as executive producers.  The mumblecore founders are always keeping their eyes peeled for innovation in independent cinema, and Tangerine – a film shot entirely on the iPhone 5S – was their calling. Tangerine reminded me of Christos Sourligas’ Happy Slapping, a film that followed hopeless teens via handheld footage shot on earlier generation smartphones.  Happy Slapping may have more interesting things to…