* New place perp instcution builder is here as build_place_perp_order_instructions_2(), ready to be moved to build_place_perp_order_instructions() when updated Mango program is deployed.
* Being able to specify commitment on the Client instead of every call.
* Better error handling (more exception details, and specific rate limiting exceptions)
* More obvious return values, instead of always having to dereference "result".
* 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.