$ git clone git@github.com:davygora/exchanger.git
$ cd exchanger
$ bunlde install
$ ruby app.rb>>Exchanger.exchange(100, '2016-10-26')
=>109.25
or
>>Exchanger.exchange(100, [Date.yesterday, Date.today])
=> [105.47999999999999, 107.65]
>>Exchanger.exchange(100, [Date.yesterday, Date.today-10.day]
=> [105.47999999999999, 106.14]
>>Exchanger.exchange(100, [Date.yesterday, '2016-10-26', Date.today - 10.day])
=>[105.47999999999999, 109.25, 107.65] $ ruby app_test.rb