Initial effort to add Bitfinex Total Return Swaps capability to XChange.
This implementation currently has tested the raw functions related to 
getting the active swaps order book, sending offers (a swap order in BFX
API terminology), retrieving responses, and cancelling offers. This work
has not been exposed through the generic TradeServices as I would like
to make sure that it is acceptable to add these loan types to the
generic interfaces (and have a bunch of NotImplementedExceptions).
Merge remote-tracking branch 'upstream/develop'

Conflicts:
	xchange-bitfinex/src/main/java/com/xeiam/xchange/bitfinex/v1/service/polling/BitfinexTradeServiceRaw.java
Add example lend book demo
Make sure the print statement accurately describes the USD swap order
book
Include appropriate MIT header
ensure comment correctly states BFX as the exchange we're retrieving the
instance of.
Merge remote-tracking branch 'upstream/develop'
Merge remote-tracking branch 'upstream/develop' into develop
Remove MIT headers. Add an offer demo class to demonstrate the new offer
functionality including getting active credits, place floating/fixed
rate offers, get offer statuses, and cancel floating/fixed rate offers.
Merge pull request #565 from evdubs/develop

Addition of Bitfinex Swaps