Drop unused h5netcdf dependency. Make matplotlib, geopandas optional dependencies.

Add new extras for optional dependencies: impactlab-tools[viz], impactlab-tools[complete].

Minor code cleanup, style update.

Update ruff lint section format in pyproject.toml.

Minor update to docstr examples to match xarray > 2023.12.0.

Drop Python 2 support. Requires Python >= v3.7.

General documentation build update. Update to readthedocs v2 configuration.

Update package dependencies. Require previously unlisted dependencies: h5netcdf, geopandas, matplotlib, numpy, pandas, scipy, xarray.

Fix error from bad coordinate assignment in impactlab_tools.gcp.reindex.hierid_to_shapenum().

Remove dependence on toolz package.

Quick and dirty code style cleanup.

Replace flake8 with ruff for code quality checks.

Consolidate requirements files into requirements.txt, purely used for Github Actions CI.

Update and refactor into src/ layout with pyproject.toml. Radically simplify the 'meta' of building and maintaining the package.

Drop tox.

Add LICENSE file to repo.

Remove Travis-CI configurations. Use Github Actions for CI (:issue:468)