Added stub implementation for notifyBid.
Added testing components.
Moved tests into implementation modules, this allows them access to un-exported features.
Fixed tasty version number in library.
Removed clutter from test main.
Added arbitrary instances for Order and composit parts.
Added sample (useless) test.
Arbitrary instances for OrderBook and price limited Orders.
Fixed lack of distinction between asks and bids in fill stage.
Merge branch 'testing'