Adding an implementation of `ssn` provider for the it_IT locale.

This implementation generates fake syntactically correct italian fiscal codes.
The checksum character is calculated accordingly to
http://en.wikipedia.org/wiki/Italian_fiscal_code_card.
Fixing a typo in comments
Removing a python 3 incompatible instruction.
Merge pull request #120 from domtes/features/it-ssn

Adding an implementation of `ssn` provider for the it_IT locale.