At about this time last year, an Obie Award winner and two-time Pulitzer Prize finalist, Brendan Jacobs-Jenkins, made his Broadway debut as primary playwright with “Appropriate,” a blistering tragicomedy tracing the reunion of a glaringly dysfunctional family. Leslye Headland, who covers similar terrain in the new “Cult of Love,” is more widely known for her television and film work than her stage outings — though I suspect that’s about to change.