Mauritania IBAN parsing rules

Examples

    iex>  %IbanEx.Iban{
    ...>    country_code: "MR",
    ...>    check_digits: "13",
    ...>    bank_code: "00020",
    ...>    branch_code: "00101",
    ...>    national_check: "53",
    ...>    account_number: "00001234567"
    ...>  }
    ...>  |> IbanEx.Country.MR.to_string()
    "MR 13 00020 00101 00001234567 53"