Psifr

This version adds statistics to measure the extent of category clustering in recall sequences.

* Added `fr.category_clustering`, which calculates list-based clustering (LBC) and adjusted ratio of clustering (ARC) for free-recall data.
* Added unit tests for LBC and ARC based on published papers.

This version adds support for analyzing prior-list intrusions. It also adds tools for working with semantic distance analyses. The documentation is expanded with examples for most functions.

* Marking of prior-list intrusions and analysis of the list lag of prior-list intrusions.
* Documentation of semantic distance analyses in the user guide.
* A utility for generating datasets from study and recall lists.
* Tools for working with semantic distance measures.
* Examples to illustrate most functions.
* Style reformatting using Black.
* A change to the automated testing system to use GitHub Actions.

This version adds support for block lag CRP analysis, which measures lags between blocks of serial positions. It also improves the flexibility and consistency of some utilities.

* Support and unit tests for block lag CRP analysis.
* Support for changing the lag field in lag-CRP analysis and determining whether counted possible transitions are transition-unique or not.
* Change to list splitting for better consistency. Now item queries are applied to both study and recall events instead of just study events, except in the context of a transition analysis.
* Added documentation on item and transition filtering.

This version fixes a problem with the `count_unique` option in the distance CRP analysis. It also adds support for counting non-unique lags, which will be necessary for implementing a block CRP analysis.

* Using the `count_unique` option for `psifr.fr.distance_crp` will now only increment each distance bin as possible once per transition. Previously each unique possible distance value was recorded for each transition, rather than each unique possible distance bin.
* A `count_unique` option has been added to `psifr.transitions.count_lags` to handle cases where multiple possible transitions may have the same lag.
* A configuration file for Zenodo has been added to set project information automatically.

This version adds more documentation and does work behind the scenes to better organize the code and make writing extensions simpler.

* Refactor all unit tests to use pytest instead of unittest.
* Reorganize unit tests to be more consistent and to remove redundant fixtures.
* Modernize the build system using updated standards.
* Reorganize the core analyses to separate measures, transitions functions, and outputs functions. The high-level `psifr.fr` API remains the same, so this change only affects development of new analyses.
* Make code style consistent by reformatting using Black.

This release is primarily to trigger archiving on Zenodo. It will also be the tagged version for the JOSS paper.

This update adds:
* A quickstart section to the README illustrating how to create and plot a serial position curve.