Implemented CurrencyPairConfiguration#doubleToBigDecimal.
Renamed a test in FXRateTest to reflect the change in approach.
Added .DS_Store to .gitignore.
Updated Money to use FXRate when doing conversions.
Removed getBuy/SellRate() in MoneyChanger and MoneyConversionTest.

Money uses MoneyChanger#getFXRate() now.
Cleaned up InMemoryMoneyChanger to reflect change in MoneyChanger.