kibbutz.lisp

This program keeps track of shared expenses for group of people and will
calculate debt or credit of each individual.

Lazy Instructions:
- Add your expense or payment to "account.sexp" following the syntax and
  conventions therein.
- run `run-account.sh' to display the debt list
- write a check
- commit the updated account.sexp file

Bugs:
- Does not account for inflation/interest rates
- SBCL doesn't seem to follow the standard 2-decimal-places for the ~$ format
  specifier
- Need to calculate repayments instead of just debts.  This seems NP-hard,
  though.

Authors:
- Neil Dantam