Lsqfit

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- New fitter lsqfit.vegas_fit that uses Bayesian integration rather than minimization.

- Small changes to tests and examples to account for new formatting of GVars (v12.0).

- More robust (and simpler) implementation of lsqfit.__version__ --- no longer
uses importlib.metadata, which is buggy.

- Documentation on how to compile with the GSL library (ie, don't use the lsqfit wheels).

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- New installation code so that it works on Python3.11 even when numpy
is not installed, and on systems with old versions of numpy.

- Adds Python wheels to PyPi distribution.


Version 13 2022-11-01
======================
Minor changes except that pickling works better now. This
means that multiple processors can be used when doing
Bayesian integrals using the vegas module's PDFIntegrator
(ie, with nproc>1) and the fit's PDF fit.pdf(p). This is useful
because fit.pdf(p) can be quite costly to evaluate when fits
are complicated.

- fit.pdf(p) is now normalized so that fit.pdf(fit.pmean)=1.
This differs from previous versions. To get the old
normalization use fit.pdf(p)/exp(fit.pdf.lognorm). This
change was made because exp(fit.pdf.lognorm) can easily
overflow when fits involve lots of parameters.

- New function fit.dchi2(p) replaces fit.evalchi2(p) and
fit.logpdf(p), which are deprecated.

- empbayes_fit has a new keyword p0 which specifies the
fit-parameter starting point for the first fit; p0
is set automatically in subsequent fits to optimize
fitting (unless it is specified by fitargs(z)).

- Fix to show_plots() to accommodate a change in Matplotlib.

- Forces Cython to regenerate *.c files when using Python 3.11 or later (deals
with incompatibilities introduced by 3.11).

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- Fixes installation issue with Python 3.10.

- Documentation fixes (thanks to Nolan Miller and Evan Berkowitz).

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Bug fix for lsqfit.gammaQ when gsl is not installed.

Version 12 2021-08-14
======================
- Removes BayesIntegrator (and BayesPDF). It is replaced by
the more capable PDFIntegrator in the vegas Python module.

- Adds two new methods to nonlinear_fit: logpdf(p) and pdf(p).

- Fixed minor bug when GSL not installed and maxit=0.

- Fixed bug involving noise parameter when no prior used.

=======================
Small update to fix a bug and add a feature. Thanks to Nolan Miller
for both.

- Fixes bug in empbayes_fit(z0, ...) when z0 is or contains integers
instead of floats.

- MultiFitter.lsqfit has a new keyword, chained. If chained=True
chained_lsqfit is used in place of lsqfit.

- MultiFitter objects have a new method MultiFitter.empbayes_fit that
is analogous to lsqfit.empbayes but for MultiFitters.

=========================
Minor update responding to a feature request.

- fit.evalchi2(p) evaluates the chi**2 for the fit at an
arbitrary value p for the fit parameters.

- Bug fix so maxit=0 works again.