Musical spoofing spicy novel ‘Fifty Shades of Grey’ to hit Manhattan theater

They promise a spanking good show. A musical spoofing the spicy bondage romance novel “Fifty Shades of Grey” is set to hit a Manhattan theater this week — featuring singing, dancing and plenty of sexual innuendo. The show, “50 Shades! The Musical,” will be performed Friday and Saturday at the Gramercy…