Barcode validator

Hi!
I just wrote a tiny validator for barcodes (EAN 13 only for now). Feel free to merge it or give me some guidelines for further development ;)
Pierre-Baptiste.
Do we need to raise.or shouldn't we just add an error to the list of errors?

IMHO, most Ruby developers don't really check for exceptions, so you'll end up bubbling an exception up to the first caller. :-(