Stick to your knitting. It's an expensive lesson that Avon has learned as the company sells the Silpada jewelry business back to its co-founders and their families for $85 million, well below what it paid three years ago. The families of Silpada co-founders Jerry and Bonnie Kelly and Tom and Teresa Walsh, through their company Rhinestone Holdings Inc., were the highest bidders in an auction process for the business. Avon announced earlier this year that it was reviewing strategic options f...