Add a few countries and fix existing patterns 🌐

[sunny]

Replaces #30.

To use it your project add the following in your Gemfile:

# International Bank Account Number validation.
# Using fork to add a few countries and fix existing patterns.
# https://github.com/iulianu/iban-tools/pull/31
gem "iban-tools",
    github: "sunny/iban-tools",
    branch: "add-more-countries-and-fixes"