Bayes-spec

- Update installation instructions because `pymc` must be installed through `conda`
- Pin python to `>3.11` https://github.com/tvwenger/bayes_spec/issues/18

Package `versioneer.py` with source.

- Refactors model parameter access. Instead of user-defined `model.cloud_params`, `model.baseline_params`, `model.hyper_params`, and `model.deterministics`, adds automatically populated attributes `model.cloud_freeRVs`, `model.cloud_deterministics`, `model.baseline_freeRVs`, `model.baseline_deterministics`, `model.hyper_freeRVs`, and `model.hyper_deterministics`.

Release for publication