Add onChange event for CC validation #2801

To reproduce the issue, when in the checkout form:

1) You go and insert a credit card number, let's say: `4242 4242 4242 4242` (VISA). On the .card-type element, the class is set to visa. Everything is ok until now.

2) Let's say you remembered that you didn't have enough funds on that card, and you want to clean up the field and insert your Master Card instead: `5555 5555 5555 4444` - **If, and only if**, you copy-paste the entire number, then .card-type concatenates the different classes because the `edd_validate_card()` function is not triggered.

`<span class="card-type visa mastercard"></span>`

Proposed modifications:
```javascript
$body.on('keyup change', '.edd-do-validate .card-number', function() {
        edd_validate_card( $(this) );
 });
```

Modified both: regular version and minified.