Upgrade pyproj requirement from 1.9.6

[danielolsen]

pyproj v1.9.6 is only compatible with Python 3.7 and lower. (see https://pyproj4.github.io/pyproj/stable/history.html#id20)

We want to be able to run with Python 3.8 and above, so we need to upgrade to at least pyproj 2.x, if not the new 3.0.

Looking at wheat we did in PostREISE (Breakthrough-Energy/PostREISE#154), there's not a perfect 1:1 translation to our usage here, since PostREISE had projections based on EPSG reference systems, while we've got a projection based on a PROJ string. It seems like using these strings, rather than an EPSG or similar, is gently advised-against (see https://proj.org/faq.html#what-is-the-best-format-for-describing-coordinate-reference-systems), so if it's easy to use an EPSG reference system then maybe we can kill two birds with one stone.

[danielolsen]

Somehow, the CI tests on the server have no problem with the current lockfile (using Python 3.8.7).

Running Python 3.8.3 locally on Windows, I get an error trying to pipenv sync or pipenv sync --pre using the current develop. I created a branch that can be used in the meantime (daniel/no_pyproj) via:

pipenv sync --python 3.7
pipenv uninstall pyproj --skip-lock
pipenv lock --pre

This branch will pipenv sync and all `python -m pytest -m "not integration" works successfully using Python 3.8.3 on Windows.