* t/09-check_digit.t: adding tests against the 'check_digit' attribute
* lib/Biblio/Record/USBC.pm: first increment to pass the tests against the 'check_digit' attribute
* lib/Biblio/Record/USBC.pm: refactoring the class to remove duplicate code
* t/00-first_design.t: refactoring the test to use the module
* t/00-first_design.t: creating a Biblio::Record::USBC by hand
* t/08-publisher.t: correcting a typo
* lib/Biblio/Record/USBC.pm: keeping only the first seven characters of a computed title
* lib/Biblio/Record/USBC.pm: correcting the logic of the computed_edition method
* lib/Biblio/Record/USBC.pm: correcting the logic of the computed_publisher method
* lib/Biblio/Record/USBC.pm: first version of the 'get_usbc' method
* lib/Biblio/Record/USBC.pm: creating a method to update weight attribute after a title modification