There is something about walking into Costco in the summer that turns even the most disciplined shopper into a "well…it's seasonal" person. One minute you are grabbing paper towels and sparkling water off your list, and the next you are loading a cart with snacks, ice cream and whatever they happen to be sampling that day. Summer is arguably Costco's most dangerous season for impulse purchases, mostly because the warehouse giant knows exactly what shoppers want this time of y