Bolivian localization

Simple adds the currency for Bolivia.

As a workaround in my code I was doing to setup moneyed with a new Currency the following:

    import moneyed
    from moneyed.localization import _FORMATTER
    from decimal import ROUND_HALF_EVEN

    BOB = moneyed.add_currency(
        code='BOB',
        numeric='068',
        name='Peso boliviano',
        countries=('BOLIVIA', )
    )

    # Currency Formatter will output 2.000,00 Bs.
    _FORMATTER.add_sign_definition(
        'default',
        BOB,
        prefix=u'Bs. '
    )

    _FORMATTER.add_formatting_definition(
        'es_BO',
        group_size=3, group_separator=".", decimal_point=",",
        positive_sign="",  trailing_positive_sign="",
        negative_sign="-", trailing_negative_sign="",
        rounding_method=ROUND_HALF_EVEN)