Add documentation on the consequences of NumPy matching C's integeer hierarchy.

[adamreichold]

Closes #404

[adamreichold]

@jeertmans Something like this?

[jeertmans]

Looks perfect @adamreichold, thanks! One last question: where would it reflect on the docs.rs pages? I don't see where the src/dtypes.rs module is documented, and that would be sad to have to go through the source file to get that information, imo :-)

[adamreichold]

One last question: where would it reflect on the docs.rs pages? I don't see where the src/dtypes.rs module is documented, and that would be sad to have to go through the source file to get that information, imo :-)

This the documentation of the Element trait. I did consider putting on into the top-level section but the topics seems to niche IMHO. That trait is the center piece for matching NumPy data types and Rust types, so it seem the most appropriate yet still discoverable item to attach this to.

[jeertmans]

Ok I understand :)

looks good to me then!
Thanks for your help and work!