Particle

* Better handling of LaTeX to HTML conversions of particle names.
* Added the tabulate package dependency to the zipapp.

* Added ``Particle.dump_table(...)`` method.
* Added tests for default/dummy particle (PDG ID = mass = 0).
* Demo notebook updated.
* Doctests introduced in the CI.
* Dependency on package ``six`` removed.

* Added the 2019 PDG data table, now default.
- Some poorly established particles not in the current PDG data files
were previously erroneously made available. They have now been removed.
* Changes in API:
- ``Particle.table()`` renamed to ``Particle.all()``.
* Enhancements to ``Particle`` class:
- Numerous LaTeX particle names updated.
- Correctly deal with experimental width upper limits.
- Better display of lifetimes and widths.
- More tests.
* Demo notebook added, with a launcher for Binder in the README.
* Extra tests for particle searches.

* Setup improvements.
* zipapp CI added.
* Particle search methods made robust against exceptions.

* Searches given a .dec decay file particle name:
- Speed-up of searches.
- Corner cases dealt with.
- Extended test suite for the ``Particle.from_dec(...)`` method.
* Added Particle.is_self_conjugate property.
* Bug fix in the PDG extended file from 2008 (in excited K, D and B meson names).

* Added re-release of the 2018 PDG data table (neutrinos added, formatting fixes).
* CI scripts for Azure enhanced.
* Test coverage improvements.
* Wheel now available on PyPI.