Britney Spears and Kevin Federline aren't going to let a divorce squabble curb their fun out in public. Both were out on the town Wednesday night, showing off happy, relieved faces. Spears, who has been photographed at several outings in New York this week, stopped by the Sony Music Studios at 1 a.m. Thursday sporting a black micro-mini dress and what appeared to be a wedding band. Federline, 28, took the stage at Chicago's House of Blues to announce, "You know who's about to be a free man, right?" His left ring finger was bare. On Tuesday, Spears, 24, filed for divorce after two years of marriage. Wednesday, Federline filed divorce papers, too. Both want legal custody of their sons, 13-month-old Sean Preston and 8-week-old Jayden James. As Federline struggles with his musical aspirations — album sales are low and tickets to his shows are being given away — Spears is making clear career moves: •She has been working in the studio since the Sept. 12 birth of son Jay...