RubyMoney/money — pull request #430 by eadz (2014-09-05 01:53:48+00:00)
Title: Add currency pair

Adds a CurrencyPair object to represent a pair of currencies.

example

```ruby

AUDNZD = Money::CurrencyPair.new(:aud, :nzd) #

AUD = Money::Currency.new(:aud)
NZD = Money::Currency.new(:nzd)

AUDNZD = Money::CurrencyPair.new(AUD, NZD) #

# Currency#/ method
AUDNZD = AUD/NZD #

# wrap method
AUDNZD = Money::CurrencyPair.wrap('AUDNZD') #

AUDNZD.to_s # "AUDNZD"
AUDNZD.base #
AUDNZD.inverse.to_s # "NZDAUD"
```

This is a starting point, I think at some point the Exchanges use representations of currency pair rates. Interested in feedback!