Fix validation for end-of-month card expiry

A card that was issued in UTC-1200 with an expiry of 02/13 is currently considered expired after 2013-03-01 00:00:00 UTC (which this code uses for validation), rather than 2013-03-01 12:00:00 UTC as should be the case.  This PR relaxes the validation to permit any card expiring in 02/13 to be considered valid until 2013-03-01 13:00:00 UTC. 

Includes a couple new tests to ensure:
1) that this works on the first day of the month
2) that we're not relaxing validation beyond the first day of the month (i.e., it doesn't work on the second day of the month)