* This is a big change that touched most files in the project.
* Library code is now an actual package, in /mango.
* Pure .py files used for shared code - easier to edit/debug, and should ease move to installable package later.
* Removed many notebooks. The remaining notebooks are useful 'display'/'show' notebooks for investigating Mango objects.
* More tests! The test story is now much improved, but more unit tests are still needed.
* There's now a Makefile for project operations.
* ReportingAccountLiquidator wraps an AccountLiquidator but provides before-and-after logging and reporting.
* Sped up fetch_token_prices() by reducing it to one network fetch
* Centralised loading of ripe mangoes by creating MarginAccount.load_all_ripe()
* Clearer, more consistent use of Observables
* Added RxPy Backpressure library
* Improved container building to allow for different tags
* Added nasty patch around pyserum bug
* OpenOrders can now provide (on-demand) the pyserum representation OpenOrdersAccount
* New context methods -unwrap_transaction_id_or_raise_exception() and random_client_id()
* Added Retrier and retry_context() function
* Added TradeExecutor and SerumImmediateTradeExecutor classes to trade on Serum
Geoff Taylor