Log Message:
py-stdnum: update to 1.7

changes from 1.6 to 1.7:
* add modules for the following number formats:
  - BN (Canadian Business Number)
  - SIN (Canadian Social Insurance Number)
  - IdNr (Steuerliche Identifikationsnummer, German personal tax number)
    (thanks Mohammed Salman of Holvi)
  - Registrikood (Estonian organisation registration code)
    (thanks Mohammed Salman of Holvi)
  - Veronumero (Finnish individual tax number)
    (thanks Mohammed Salman of Holvi)
  - UPN (English Unique Pupil Number)
* fix a bug in the Czech DIČ check digit calculation
* fix conversion of 9 digit ISBN to ISBN13
* fix a bug in the Damm is_valid() function
* more validation of 13-digit ISBN values
* more validation of ISMN values
* various code and test improvements (100% branch coverage now)
* documentation improvements