COMINGS AND GOINGS>>?Tiffany & Co. promoted Andrew W. Hart to senior vice president of diamonds and gemstones. Hart has been with the company since 1999 and has served as vice president of diamonds and gemstones since 2002. The company also announced that Robert S. Singer has been elected to its board of directors. Singer has held a variety of senior-level corporate positions, including chief financial officer of Gucci Group NV. He will chair the board’s audit committee and replaces J. Thomas Presby, who reached the mandatory retirement age.>>?Ivanka Trump Fine Jewelry named Geoffrey N. Hess its new ­president. Hess was a founding member of Giu­liani Partners, the consulting firm headed by former New York City mayor Rudolph W. Giuliani. Previously, he served as the youngest senior advisor to the mayor during the Giuliani administration, and an associate at Tishman Spe