signal-based async io for rust

why?

mainly as a way of learning about the gory details of async rust, but also because i was annoyed by the fact that everything just uses thread pools.

should i use this?

probably not. it's not very portable, and it's performance is basically the same as tokio anyways.

lib.rs:

async io using SIGIO

overriding the SIGIO handler will cause futures created by this crate to hang. File implements traits from tokio, but it should work just as well with other async runtimes.

only works on regular files on GNU systems (only tested on glibc linux)