Expiry date validation does not allow MM/YY format
Expiry date validation does not allow MM/YY format

Fixes #17 and #49
nogorilla/ng2-cc-library,nogorilla/ng2-cc-library,nogorilla/angular-cc-library,nogorilla/ng2-cc-library,nogorilla/angular-cc-library,nogorilla/angular-cc-library