Photograph by David M. AllenIf you catch Theater Under the Star's Cabaret on its last weekend, and we suggest you do, here's a tip: Don't sing along with the performers. (Hair Balls was treated to a performance of "Willkommen" by a fellow audience member during our visit on opening night.) But even with an impromptu sing-a-long, this production of Cabaret is worth your attention.As Houston Press reviewer Lee Williams reported, this revival about a nightclub in 1930s Germany is "brighter and mor