Update TARDIS setup and package infrastructure

[wkerzendorf]

TARDIS's setup and package architecture is based on theastropy's excellent package template ( https://github.com/astropy/package-template) this has changed in the last years and we should update our infrastructure to follow the new guidelines. We should also look out for this https://github.com/astropy/astropy-APEs/blob/master/APE17.rst. Once things are changed we need to add these files to be excluded from codestyle black changes.

[epassaro]

Some considerations:

• Maybe would be nice to implement it before on carsus since it's a smaller package to learn how it works
• tardis still have montecarlo Cython code included (is this the only compiled extension, right?). Would be nice to ditch this before moving to new astropy template
• Moving to the new template should be done before moving on conda-forge (or any form of packaging) otherwise we will doing the same job twice

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25/01/2021

• Also I found the new template uses setuptools_scm. This package allows setting versions according to git tags. This seems very conveniently, but unfortunately has some caveats. For example, it does not work if tags have the dev word on it. This would break our CI release cycle because our tags have the word dev.

[epassaro]

Already moved carsus to the new package infrastructure, this could be done soon.

[epassaro]

Closed by #1674