Sometimes, nature is a bitch. It's not evil, it just is -- you can't call a lion an asshole for eating that gazelle and a parasite isn't exacting some cruel vengeance against its host, but the predator's lack of moral culpability doesn't make the food chain any less painful for the prey. Lorcan Finnegan's sophomore feature Vivarium is all about the ravages of life cycles, natural and man-made, from the intimate perspective of a couple experiencing the peaks and valleys of the 21st Century human life cycle in fast-forward, while literally trapped in …