adding OrderAcknowledgement class
corrected OrderAck spelling
Merge branch 'master' into add_order_ack
formatting
added Orders validations
Modified Query to format MarketplaceIds properly

Previously, the Query class dealt with market & markets differently.
However, according to the Amz MWS specification 'MarketplaceIdList.Id.n'
is not valid.  A list of markets should be specified like 'MarketplaceId.Id.1',
'MarketplaceId.Id.2'.
removed duplicate code
corrected shipping_address for Orders
added more detail to Orders
added ShipmentServiceLevelCategory to Order
Merge branch 'master' into add_order_ack

Conflicts:
	lib/mws/query.rb
added SellerOrderId
renamed send_order_acknowledgement
updated Orders send_acknowledgement to accept 'items'
Merge pull request #3 from rnhurt/master

Added order_acknowledgement to Orders class