Like the couple it’s about, “Slow” acknowledges and, to some degree, gives in to expectations set by a world overloaded with conformist-minded romcoms and conventional relationship blueprints. But it’s worth seeing. And for a weeklong run starting Friday at the Gene Siskel Film Center, Chicago audiences can see for themselves. Simple, efficient set-up here, in Lithuanian writer-director Marija Kavtaradze’s second feature.