Some logging events

* When pay.gov makes a callback, log the success or failure
* Make sure to delete donor info when above callback is a failure
* When clearing stale donor information, log how many were removed
* When synchronizing account information, log when a new account is added, updated, or a failure occurred (due to invalid country/sector)
* Remove the reliance on the 'tests.yaml' fixture from the synchronization tests. Locally that sped test execution from 35s to 22s
That's a good question -- I'm not too sure how common canceled transactions are. Let's bet on uncommon; I'll change this to a warning.