Add Bayesian AB test (fixes #45)

[jvivian]

• Add raw values to output (fixes Saving the raw input for each state in the same subdirectory #42)

[codecov]

Codecov Report

Attention: Patch coverage is 89.28571% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 95.8%. Comparing base (85ab016) to head (cf1e9df).

Files	Patch %	Lines
covid19_drdfm/processing.py	75.0%	1 Missing and 1 partial ⚠️
covid19_drdfm/dfm.py	95.0%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main     #46     +/-   ##
=======================================
- Coverage   97.7%   95.8%   -2.0%     
=======================================
  Files          5       5             
  Lines        180     191     +11     
  Branches      35      35             
=======================================
+ Hits         176     183      +7     
- Misses         2       5      +3     
- Partials       2       3      +1     

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