feat(build): build abi3 wheels

[lukapeschke]

This simplifies our wheel build process by using the abi3 API.

https://pyo3.rs/v0.14.5/building_and_distribution#py_limited_apiabi3

It allows us to build only a single wheel per target OS/arch.

closes #168

[lukapeschke]

Good news: There's ansolutely no performance impact :tada:

before

after