* made a paradigm "regression", preparing for a 3.4.0 release
* felt CA was becoming way too complicated
* grscheller.datastructures needed it to fully embrace type annotations
* but I was shifting too many features back into grscheller.circular-array
* want ca to be useful for non-functional applications
* changes made
* removed grscheller.fp dependency
* remove _sentinel & _storable slots from CA class
* remove copy method, just use ca2 = CA(*ca1) to make a shallow copy
* adjust __repr__ and __str__ methods
* experimenting with Spinx syntax in docstrings (still using pdoc3)
* changed nomenclature from "left/right" to "front/rear"
* unsafe and safe versions of pop & fold functionality
* left and right folds improvements
* consolidated `foldL, foldL1, foldR, foldR1` into `foldL` & `foldR`
* TODO: rename `foldL` to `fold_forward` & `foldR` to `fold_backward`
* tests working
* basically I changed pops to unsafe pops and added `try except` blocks
* safe versions tests needed
* safe pops return multiple values in tuples
* will take a `default` value to return
* if only asked to return 1 value and CA is empty
* seems to work properly from iPython