Problem validating the checksum

In this line

```
number[0].chr.to_i == (10 - ((odd * 3) + even) % 10)
```

the result on the right side can be 10 which is != 0. Shouldn't it be

```
number[0].chr.to_i == (10 - ((odd * 3) + even) % 10) % 10
```

then?!

Thanks for the code anyway.

Cheers,

Robert
