Expect to hear a lot more in the coming months about a Waltham company called SavingStar and its quest to rid the world of paper coupons. After growing at a faster rate than digital giants such as Groupon and Foursquare, SavingStar just secured $9 million in its third round of financing. Now, the company is likely on the cusp of becoming a household name. A provider of digital coupons, SavingStar is a simple way to save a few bucks every time you shop for groceries at any of the thousands of stores it has partnered with.