Build wheels with minimal supported numpy versions

[rth]

Generally libraries linked against numpy are forward compatible, meaning that wheels should be generated with minimal numpy versions (here. 1.17) and they will be compatible with following numpy versions.

The current situation of generating wheels with latest numpy means that earlier numpy version might not work.

This means that for building wheels and testing different numpy versions could optionally be used.

This is discussed for instance in https://conda-forge.org/docs/maintainer/knowledge_base.html?highlight=numpy#building-against-numpy the idea is similar when building wheels (see e.g. https://github.com/matthew-brett/multibuild)

If your project depends on NumPy, you will want to build against the earliest NumPy that your project supports - see forward, backward NumPy compatibility.