Dart pub warning fixes (#19)

* Version bump prep

* Update pubspec.yaml

* Warning fixes from dart pub

Author: Tanner Davis

lib/card_number.dart

@@ -10,9 +10,6 @@ import 'validation_results.dart';
 /// Validates the credit card number and determines
 /// the credit card type as well
 
-/// The default card number length. Set to 19
-const int _DEFAULT_MAX_CARD_NUM_LENGTH = 19;
-
 /// Default string returned on a failed validation
 const String _DEFAULT_FAIL_MESSAGE = 'Invalid credit card number';
 

lib/postal_code.dart

@@ -7,7 +7,7 @@ import 'validation_results.dart';
 /// service like Stripe or Braintree for that.
 
 /// The default minimum postal code string length. Set to 3
-const int _DEFAULT_MIN_POSTAL_CODE_LENGTH = 3;
+// const int _DEFAULT_MIN_POSTAL_CODE_LENGTH = 3;
 
 /// Checks if the postal code seems legit
 ValidationResults validatePostalCode(String postalCode, {int? minLength}) {

test/card_number_test.dart

@@ -44,17 +44,6 @@ void main() {
     SecurityCode.cvv(),
   );
 
-  // Conflicts with typical Visa card
-  final CreditCardType conflictingCardType = CreditCardType(
-    'conflict',
-    'Conflict',
-    [16], // only length 16
-    {
-      Pattern(['4'])
-    },
-    SecurityCode.cvv(),
-  );
-
   final String someMadeUpCCNumFull = "9999 6614 3472 7891";
   final String someMadeUpCCNumPartial = "9999 6614 3472";
   final String modifiedVisaCCNumFull = "3538243039991295";