Typecats

Added new exception hook functionality for better visibility into
structuring errors. By default adds verbose logging when your item
fails to structure, but this default behavior may be replaced.

New converter which will strip (recursively) all attributes which are
equal to their attrs defaults, except for attributes annotated as
`Literal`, which are assumed to be required.

Can be called using `unstruc_strip_defaults(your_attrs_obj)`, or on a
Cat type using the new boolean keyword argument on `unstruc`,
`your_cats_obj.unstruc(strip_defaults=True)`.

No longer assume that the `dict` methods will not be overlaid on a
Wildcat by `attrs` attributes.

Extracted the default `cattrs` Converter from all implementations to
make `typecats` fully compatible with the use of any
application-provided Converter(s).

All that is necessary to use an externally-supplied converter is to
call the new `patch_converter_for_typecats` function exported by the
package root on the Converter. This will patch your Converter to
enable `typecats` functionality while still maintaining all the
existing functionality and previously-registered function-dispatched
structure and unstructure hooks within your Converter.

Reworked Wildcat functionality to use a cleaner hooking process.

Corrected return type of `try_struc` to be `Optional[T]`.