+0.36 Tue Jun 14 11:36:05 PDT 2016
+ - Allow (and doc) import of receipt_cardtype
+ - validate_card() is a new synonym for validate(), starting a long-term
+ plan to stop exporting validate() or anything else by default.
+ - Best-effort cardtype() when only the first two digits are available
+ (identify masked 60xx as Discover)
+