Add Japan support

[mkokio]

Contributing a new country ?

• Have you checked to ensure there aren't other open Pull Requests for the same country?

1. Create a new class in the Countries directory. It should extend the Country class. Done.
2. Add a test for the new country in the tests directory. Done.
3. Run the tests so a snapshot gets created. Done.
4. Verify the result in the newly created snapshot is correct. Done.

[Nielsvanpach]

Thanks!