But don’t forget the most important piece: you have to make it easy. Sounds like an impossible task, but Cambridge, Mass.-based Edhance is convinced it has the ability to make it all happen at once, and it’s as simple as swiping your debit card. “We’re building a merchant network to ensure we can offer a lot of good deals,” explained Bjorn Larsen, president of Edhance. “Then we let students know it’s free to join with us; they just sign up, register their credit or debit card, and start saving....