Slovenia IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "SI",
    ...>    check_digits: "56",
    ...>    bank_code: "26",
    ...>    branch_code: "330",
    ...>    national_check: "86",
    ...>    account_number: "00120390"
    ...>  }
    ...>  |> IbanEx.Country.SI.to_string()
    "SI 56 26 330 00120390 86"