editing http://en.wikipedia.org/w/index.php?title=International_Standard_Book_Number, section “ISBN-13 check digit calculation”

page edits:
“/* ISBN-13 check digit calculation */ made Ruby checksum code more idiomatic (and easier-to-read)”
http://en.wikipedia.org/w/index.php?title=International_Standard_Book_Number&diff=prev&oldid=510791284

“ refactored Ruby code for clarity”
http://en.wikipedia.org/w/index.php?title=International_Standard_Book_Number&diff=510791920&oldid=510791284