Dtools.datastructures

* works with all the current versions of fp and circular-array
* preparing for PyPI 0.21.0 release

* updated to use grscheller.fp.nada instead of grscheller.untyped.nothing
* made debugging tons easier
* updated to use all latest PyPI versions of dependencies
* three failed tests involving class SplitEnd
* putting off PyPI v1.0.0 release indefinitely
* all dependencies need to be at v1.0+
* need to work out SplitEnd bugs
* still need to finalize design (need to use it!)
* need to find good SplitEnd use case
* other Stack variants like SplintEnd??? (shared data/node variants?)

* updated to use grscheller.circular-array version 3.3.0 (3.2.3.0)
* updated to use grscheller.fp version 0.3.0 (0.2.3.0)
* removed grscheller.circular-array dependency from datastructures.SplitEnd
* still preparing for the 1.0.0 datastructures release
* as I tighten up typing, I find I must do so for dependencies too
* using ` type: ignore` is a band-aid, use `overload` and `cast` instead
* using `overload` to "untype" optional parameters is the way to go
* use `cast` only when you have knowledge beyond what the typechecker can know

* first devel version requiring circular-array 3.1.0
* still some design work to be done
* gave Class SplitEnd fold and fold1 methods
* TODO: Verify flatMap family yields results in "natural" order

* have begun relaxing the requirement of not storing None as a value
* completed for queues.py
* requires grscheller.circular-array >= 3.0.3.0