refactor tests, add some comments
acceptance test 5 passes
acceptance test 6 passes (4 apples get a discount)
acceptance test 6 passes
re_commit data_cleaner tests
refactor out calculation & output formatting
further refactoring tests
more refactoring
simple refactor  is_multiple(n,2)
refactor - remember all purchases, and count_cherries from it
refactor counting function
use count purchase list not the counters
remove magic numbers
refactor: remove apple counting
refactor apple discount signature
remove no_pommes counter
remove no_bananas counter
remove no_mele counter
remove no_cherries counter
remove no_apples counter