ISBN-13 codes ending with a checksum of `0` always fail, even if valid.

Example of a valid ISBN which will get flagged as invalid: `978-3-598-21536-0`

This is caused by an unhandled edge case in `checkChecksumISBN13` in the following code:
`return 10 - sum % 10 == ( checkSum - '0' );`

The left-hand side of the equation will produce a sum which is checked against the right-hand side checksum. The sum has a possibility of resulting in the number `10` which will fail when checking against the checksum `0`.

The ISBN-13 algorithm however states that a sum of `10` should be converted to a sum of `0` before being compared to the checksum.

One possible solution could be an additional modulo operation such as `return (10 - sum % 10) % 10 == ( checkSum - '0' );` ).

Another solution could be an explicit check for `10` which resolves it to `0`.