Revert dev setup back to Makefiles

[leouieda]

The setup using nox helped with some aspects but also created a bunch of extra setup and understanding that a novice would need in order to contribute. Reverting to our old setup of a conda environment + Makefiles makes things easier to maintain across our projects.

Reminders:

• [ ] Run make format and make check to make sure the code follows the style guide.
• [ ] Add tests for new features or tests that would have caught the bug that you're fixing.
• [ ] Add new public functions/methods/classes to doc/api/index.rst and the base __init__.py file for the package.
• [ ] Write detailed docstrings for all functions/classes/methods. It often helps to design better code if you write the docstrings first.
• [ ] If adding new functionality, add an example to the docstring, gallery, and/or tutorials.
• [ ] Add your full name, affiliation, and ORCID (optional) to the AUTHORS.md file (if you haven't already) in case you'd like to be listed as an author on the Zenodo archive of the next release.

[leouieda]

As a heads up @MGomezN @dabiged @LL-Geo we're updating this now and you may have to update your forks after this is merged. Your current PRs shouldn't be affected and I'll take care of any issues there.

Really sorry for letting the project stall like that. I'm hoping to reanimate it now and will be looking to merge your PRs soon!