On a cool, breezy, fall Ann Arbor night, The Irwin Building at 315 North Main Street emits a moody Halloween blue color.  Two glowing rose-colored lamps stand tall at the entrance, where a sign reads “Wolverine Technical Staffing, Inc.”   An inflatable witch sits on the roof and a scary lady stares out from inside a window.  With Halloween still 5 days away, a group of kids dressed in costumes walk past the house toward the heart of Main Street.  Street traffic begins to slow as midnight approaches.