When her Las Vegas residency begins at the end of the month, Britney Spears should probably stay away from the roulette wheel, because numbers are not her friend at the moment. Spears’ new album Britney Jean arrived this week, moving only 107,000 copies for a fourth-place finish on the Billboard 200. It’s the weakest opening week in Spears’ career, both by hard sales numbers and chart position (previously, her slowest sales week was the opening frame of her debut …Baby One More Time, which tallied...