If you found, and stayed with, last week’s series premiere, you’ve already seen one of the fall’s best new series. If you didn’t, dive in tonight anyway, whether or not you catch up on streaming video. Last week, Rebecca (Rachel Bloom) moved to West Covina, CA to chase down an old boyfriend, only to discover, despite his Facebook status, that he has a girlfriend. Tonight, Rebecca meets that girlfriend. The encounter isn’t exactly music to Rebecca’s ears &ndash