code: function(cardNumber, success, error) {
      success = success || noop;
      error = error || noop;
      exec(success, error, "CordovaStripe", "validateCardNumber", [cardNumber]);
    }
docs: Validates card number
  @param cardNumber {String} Credit card number
  @param {Function} success  Success callback that will be called if card number is valid
  @param {Function} error  Error callback that will be called if card number is invalid