Set custom symbol for currency in Money gem

gistfile1.txt

2.2.1 (main):0[1] > Money.new(100, :RUB).currency.symbol
=> "₽"
2.2.1 (main):0[2] > show-method Money.new(100, :RUB).currency.symbol

From: /Users/max/.rvm/gems/ruby-2.2.1/gems/money-6.5.1/lib/money/currency.rb @ line 211:
Owner: Money::Currency
Visibility: public
Number of lines: 3

attr_reader :id, :priority, :iso_code, :iso_numeric, :name, :symbol,
  :disambiguate_symbol, :html_entity, :subunit, :subunit_to_unit, :decimal_mark,
  :thousands_separator, :symbol_first, :smallest_denomination
2.2.1 (main):0[5] > cd Money.new(100, :RUB).currency
2.2.1 (RUB):1[6] > show-method initialize

From: /Users/max/.rvm/gems/ruby-2.2.1/gems/money-6.5.1/lib/money/currency.rb @ line 227:
Owner: Money::Currency
Visibility: private
Number of lines: 8

def initialize(id)
# cut...
  initialize_data!
end
2.2.1 (RUB):1[7] > show-method initialize_data!

From: /Users/max/.rvm/gems/ruby-2.2.1/gems/money-6.5.1/lib/money/currency.rb @ line 416:
Owner: Money::Currency
Visibility: private
Number of lines: 17

def initialize_data!
  data = self.class.table[@id]
# cut...
  @symbol                = data[:symbol]
# cut...
end
2.2.1 (RUB):1[8] > self.class.table
=> {
  :aed => {
# cut....
2.2.1 (RUB):1[9] > self.class.table[:rub]
=> {
# cut...
                 :symbol => "₽",
# cut...
2.2.1 (RUB):1[11] > self.class.table[:rub][:symbol] = 'rub'
=> "rub"
2.2.1 (RUB):1[12] > Money.new(100, :RUB).currency.symbol
=> "rub"