Make `Flow` and `FlowEnsemble` pickle-able (#124)

Moved saving to __getstate__ and __setstate__ to enable pickle-ing

Added sample weights and initial_loss to ensemble trainer.

Moved np.trapz -> scipy.integrate.trapezoid. Updated version requirem… (

#96)

* Moved np.trapz -> scipy.integrate.trapezoid. Updated version requirements. Some linting.

* Bumped python version array in github action.

* Github action version numbers now strings.

Replaced jnp.NINF with -jnp.inf (#95)

Replaced jnp.NINF with -jnp.inf

Bumping version for fix (#91)

* Bumping version for CentBeta13 info fix

Validation (#88)

Added validation set to training.

Merge pull request #82 from jfcrenshaw/issue-81

Fix Uniform log_prob for large dimensions

Merge pull request #75 from jfcrenshaw/dev

Added some missing type annotations

Updated pyproject.toml to include info for PyPI.

Merge pull request #69 from jfcrenshaw/dev

Updated depecrated jax methods.