Alice's ATM

I finished the basic assignment, then refactored the code by pulling out similar instructions from the two withdrawal methods and turning them into a single function that takes the two accounts as parameters. The position of the arguments determines which account is the initial withdrawal target, and which is the backup account.

Ultimately, this actually made the code less readable and necessitated some superfluous instructions in the resetBoxes() function I wrote. You'll see.

Even though my second commit is DRY-er than my first, I think the first is superior.