Authorityspoke

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* Create broader conditions for Procedure.contradicts()

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* Add `__init__.py` to utils folder

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* Publish repo's utils folder as part of AuthoritySpoke package

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* Fix bug where some types of cross-references caused loading of Holdings from JSON to fail
* Update case download function because Case Access Project API no longer includes "casebody" field in all responses from cases endpoint
* `new_context` function can use string to find Factor to be replaced
* Enactment URIs can target a chapeau or continuation
* Fix bug that created [multiple pint Unit Registries](https://github.com/hgrecco/pint/issues/581)

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* Enactments may choose text by section without a TextQuoteSelector
* Remove "regime" parameter from Enactment
* Add data serialization using [Marshmallow](https://marshmallow.readthedocs.io/)
* Migrate JSON data loading functions to Marshmallow
* Add Decision class containing Opinions
* Add Explanation class to clarify relationships between Holdings
* Improve readability of string representations of objects
* Move text selectors to separate [anchorpoint](https://anchorpoint.readthedocs.io/) library
* Add [apispec](https://github.com/marshmallow-code/apispec) schema specification for Holding input JSON files

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* Merge ProceduralRule class with Rule
* Split aspects of Rule into a separate Holding class
* Use Selectors to anchor Holdings to Opinion text
* Ignore was/were differences in Predicate content text
* Let input JSON label a Rule as the "exclusive" way to get output
* Create addition operator for Factors, Rules, and Holdings
* Let Rule init method handle the necessary Procedure init method
* Use addition operator to add Factors as Rule inputs
* Use addition operator to add Enactments to Rules
* Create function to consolidate list of Enactments
* Add Union operator for Rules and Holdings
* Move functions for loading objects from JSON and XML to new I/O modules
* Add "explain" functions to show how generic Factors match up when a contradiction or implication exists
* Add whitespace to `__str__` methods for greater clarity