Arc-alkali-rydberg-calculator

This is a new release of a package to allow beta preview and testing of new functionality that arrives with ARC 3.0.0. See 33 and also beta functionality explained in new [documentation](https://arc-alkali-rydberg-calculator.readthedocs.io/en/latest/). Note that you might need to refresh documentation page in web browser to see the latest version of documentation.

This release also changed functions in old ARC code. Nothing should be broken, but if you do experience some new errors when calling old functions that used to work with ARC versions of 2.1.* and earlier, please submit issue.

Minor release that makes installation even easier by doing automatic installation of dependences via pip (see 32 ).

Introduces `arc.advanced` collection of modules that extend basic ARC functionality. Modules are contributed by the research community (and we are looking forward to more contributions!).

The first contribution is by Alessandro Greco, Dipartimento di Fisica “E. Fermi”, Università di Pisa, Italy. He created function `getPopulationLifetime` for calculating population lifetimes in Rydberg manifold and that can be loaded from `arc.advanced.population_lifetime` . See [documentation](https://arc-alkali-rydberg-calculator.readthedocs.io/en/latest/advanced.html) and [readme](/arc/advanced/README.md) for more details

Updates dependencies with Numpy (>=1.16.3) and Scipy so that new versions of libraries can be used (26).

Minor release fixes selection of basis in pair-state basis for calculations of very low states (like first excited state).
See 4e1ddbbe3075e3315469153a29b871667cb01d31 and d08ea621db8b9922f099223a195998dce86e4c92 .

Updated literature values for Caesium with values in Phys. Rev. A 94, 012505 (2016).

**For updating existing ARC version:**

* if you want to **keep your calculated dme** you have to manually copy `/arc/data/caesium_literature_dme.csv` into `~/.arc-data` on your computer;
* if you do **not want to keep your calculated dme** you can delete `~/.arc-data` folder, and on first loading of new folder will be created and populated.