Use localized amounts for Stripe

@odorcicd and @ntalbott to review. The issue is that ``stripe.rb`` used to send all amounts as-is to Stripe, whereas they require that only major units be used for currencies that do not define any minor units, i.e. ``JPY`` or ``CLP``. Remote tests pass as well.

Reimplementing an identical ``non_fractional_currency?`` bother me though, should I instead extract ``CURRENCIES_WITHOUT_FRACTIONS`` to a class method and just override that, keeping a single implementation of ``non_fractional_currency?``?