Nestpy

* New Physics Modeling:
** Skewness can be turned off and on now for ER just like for NR. For on -> old model or fixed (Quentin Riffard, LZ/LBNL)
** Older beta model is default for gaseous Xenon, a better fit to old world data at the keV scale (Eric Church, DUNE/PNNL)
** New dark matter halo model defaults, bringing NEST up to date on WIMP and Sun v (Baxter et al., arXiv:2105.00599)

* Miscellaneous Bug Fixes:
** Fluctuations adjust for difference in width from truncated Gaussians for PE not just mean
** Complaint that position resolution too poor does not activate until above S2 (top) of 40 PE
** In the dE/dx-based model the minimum LET is now 1.0 MeV/cm not 0 to avoid weirdness

* Updated binding for GetQuanta to allow for nestpy control over ER skewness.

nestpy versioning has been incremented to sync with NEST v2.4.0. Some python bindings for LArNEST functions has changed since v2.0.1

The NEST submodule has been updated to use NEST v2.3.12beta. The main changes here are:

- Moved declaration of free parameter vectors to NEST.hh and are globally defined, as opposed to being part of NESTcalc
- Introduced the ERYieldsParam vector to give more user control over the beta ER yields model
- Updated the NRERWidthParam defaults to reduce ER band widths

The nestpy bindings have been updated to take the above changes into account. Additional detector functions now have bindings included as well.

The copy/paste method for the NEST bindings have been replaced with adding NEST and other modules (such as gcem and pybind11) as git submodules which are downloaded at compile time. LXe notebooks and python scripts have been moved to tutorials/arxiv, and new notebooks will be placed in the tutorials folder as they are created in the future. LAr functionality through LArNEST has been added and will be expanded upon in future releases.

Suggestions/issues/errors should be added as github issues.

Users may have to do before installing.

pip uninstall nestpy

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What's Changed
* Integrated testing for multiple python versions by JoranAngevaare in https://github.com/NESTCollaboration/nestpy/pull/80
* No more travis, pipy uploads via github actions by JoranAngevaare in https://github.com/NESTCollaboration/nestpy/pull/86
* Thanks to the great help of Joran Angevaare, we now use GitHub Actions and no longer use Travis for releases and testing.
* `pip install nestpy` works again.
* Should one want to recompile from source, you will still need to use `git clone` (for now).


New Contributors
* JoranAngevaare made their first contribution in https://github.com/NESTCollaboration/nestpy/pull/80

**Full Changelog**: https://github.com/NESTCollaboration/nestpy/compare/v1.5.2...v1.5.4