Buttonwood

Merged in same changes that were made in 1.0.7.

A quick release with minimal changes that fixed issues arising from poor branch management.

Newest release:
- created a PriceFactory
- changes interface for Market to require a PriceFactory and optionally allow for qty settings
- moves MPI from product to price factory and allows you to get at it from Market, which is a better construct
- added some efficiencies in a few places
- added the first examples to the source code (but not the packaging)
- add some helper functions and event tracking to Subchain
- and more! (a full list can be found at https://github.com/nabicht/Buttonwood/milestone/1?closed=1)

1.1 will be the last supported release on python 2.x

Fixed a variety of issues that prevented a partial fill from closing a subchain and chain if it took the current exposure to 0.

Fixed an issue with the creation of a subchain reason. Fully filled new subchains (from a new order) were not getting marked as new subchains because of a cancel replace. This has been fixed.

Made some changes to Aggressive Impact Listener so it won't break if handling an event for a market it doesn't care about.