windmil reader not compatible with networkx version in setup.py

[nlaws-camus]

setup.py specifies major version 2 of networkx, but the code in the windmil reader is only compatible with v1 of networkx (and possibly other parts of ditto)

for reference
https://networkx.org/documentation/latest/release/migration_guide_from_1.x_to_2.0.html