Drop Tank is a small company in footprint — it started with only 22 people — but it has an outsized mission: to provide loyalty and discount programs to thousands of gasoline retailers. It has been decades since gas stations offered incentives to purchase their products. Last time, in the 1960s, retailers routinely would offer silverware, glassware and china with fill-ups. Alternatively, some would offer Green Stamps — collectible coupons redeemable for merchandise. That was the state of the art for loyalty programs.