Fix benches and tests to use Cursor #6
Description
This is an interaction between potocpav/npy-rs#15, potocpav/npy-rs#16, and potocpav/npy-rs#17, all of which have effectively been merged in this fork so I can finally work on it!
Basically, potocpav/npy-rs#15 and potocpav/npy-rs#17 added a bunch of benches and tests that wanted to use Cursor<Vec<u8>> (support for which was added in potocpav/npy-rs#16).
Don't forget to remove the entries from .gitignore!