This works by extracting the date-crawling code from get_transaction() to a separate method. Now iter_transactions() will similarly make API requests with different month-long date ranges until covers the entire date range the user requested.
Outgoing payments don't have a fee (PayPal takes their fee out on the receiver's end).
This is enough code to start using the tool to debug itself, so it's time to start committing individual bugfixes.
