Currency column type

[sunblaze]

A currency column type would be very useful to have in this gem. Here's what I've used in the core to get what I was looking for.

    class CurrencyType < ActiveRecord::Type::String
      def serialize(value)
        return value.iso_code if value.respond_to?(:iso_code)
        super
      end

      def cast(value)
        Money::Currency.new(value)
      end
    end
    attribute :base, CurrencyType.new
    attribute :counter, CurrencyType.new

Would be nice if the gem also registered the type so it could just be attribute :base, :currency