Return numpy arrays from Rust

[kylecarow]

@calbaker check this out!!!

I think setting using numpy arrays already worked, so this is something we can do now:

[kylecarow]

It seems some pymethods that return Vecs (e.g. RustCycle::get_dist_m) should be changed to return numpy arrays as well, so they don't become lists on the Python side. @calbaker thoughts?