Move Icelandic symbol after the digits

[viktorsmari]

In Rails number_to_currency helper the kr symbol comes after the digits.

I might be wrong, but most of the major Icelandic online sites have the "kr." symbol after the price.

I am Icelandic and it looks odd having the kr123 vs 123 kr.

ActionController::Base.helpers.number_to_currency(12345, locale: :is)
=> "12.345 kr."

Money.from_amount(12345, 'ISK').format
=> "kr12,345"

From the rails-i18n we can see the formatting is 'number unit':
format: "%n %u"
https://github.com/svenfuchs/rails-i18n/blob/master/rails/locale/is.yml

[coveralls]

Coverage increased (+0.0002%) to 99.965% when pulling e530178 on viktorsmari:patch-1 into e6aa20e on RubyMoney:master.

[coveralls]

Coverage remained the same at 99.965% when pulling d7713b5 on viktorsmari:patch-1 into 2efd45f on RubyMoney:master.

[antstorm]

@viktorsmari this PR makes sense to me, can you please fix the specs so I can merge it?

[antstorm]

Looks good, thank you!