compile the docs. updates some RuntimeError to ValueError.

renaming PLNPCA to PlnPCAcollection and _PLNPCA to PlnPCA. Now PlnPCA is

See merge request !26

it.

public. PlnPCAcollection is a collection, I implement all the required
methods such as __getitem__ etc, and wrote tests for it.

updated tests for the from_formula init and removed setup.py to get a

See merge request !20

PLNPCA with the previous instance of coef and _components. Much much
faster.

pyproject.toml

Dev

See merge request !19