Migrate from `tokio 0.1` to `tokio 1`

[str4d]

This is going to be absolutely hellish. I started ire in 2017 as a way to learn Rust, and decided the best way to do that was to dive head-first into 2017-era async Rust. Things have changed... a bit... since then.

[bheesham]

I tried a naive approach (incremental upgrade of tokio and futures) and there's a lot of changes.

See: https://github.com/bheesham/ire/tree/upgrade-tokio-and-friends

My changes primarily address some import changes, but there's a lot stuff like Future changed so it no longer has an Item and Error, etc (as can be seen in this gist).