Credit cards are insanely convenient. Nowadays, you don't even need to swipe your card to pay, you can just whip that little bad boy out, tap your plastic money on the terminal, and BAM, you've made a purchase. Old school folks have reluctantly accepted that everyone prefers to pay with plastic money, idealizing the old ways of counting cash and receiving change in exchange for goods or services. But with all that spare change jangling around in your pocket, wouldn't you rather...