+card. My list is not complete; I welcome additions.
+
+Possible return values are:
+
+ VISA card
+ MasterCard
+ Discover card
+ American Express card
+ Diner's Club/Carte Blanche
+ enRoute
+ JCB
+ BankCard
+ Switch
+ Solo
+ Unknown
+
+"Not a credit card" is returned on obviously invalid
+data values.