Does not handle countries with use_country correctly

[JishnuM]

Some countries, e.g Guam, Jersey, Liechtenstein do not have address_template in their config and instead have use_country to use another countries config.

The Python code does not handle this correctly and instead throws an exception at https://github.com/dunkelstern/international_address_formatter/blob/master/international_address_formatter/format.py#L53 in such cases.