Add non-standard rates

[kdeldycke]

Reduced, increased and parking rates are not included yet.

[wojtha]

There is another project with the same goal called http://jsonvat.com. Repo: https://github.com/adamcooke/vat-rates maybe you can guys cooperate?

[kdeldycke]

As explained in the README, I'm going to source the data from the EU documentation. The latter provides better historical non-standard rates.

The thing is, I decided to create this database because all the current VAT libs were quite naive about the territory definition. Most of the time it's only based on the country, while the territory a tax applies to, in a fiscal context, is a much more insidious concept carrying administrative, political and historical underlayings.