Add appropriate tokio features to Cargo.toml

[ErwanDL]

While working on routerify/routerify-websocket#3, I encountered issues when trying to build the test_stream_body.rs example, after having updated routerify-websocket to use tokio 1.x.

error[E0425]: cannot find function `spawn` in crate `tokio`
   --> ~/.cargo/git/checkouts/stream-body-094892f572609189/4ca8d42/src/body.rs:104:16
    |
104 |         tokio::spawn(async move {
    |                ^^^^^ not found in `tokio`
    |
help: consider importing one of these items
    |
1   | use crate::body::io::async_write::io::sys::ext::net::raw_fd::sys_common::util::thread::spawn;
    |
1   | use std::thread::spawn;
    |

error[E0425]: cannot find function `copy` in module `io`
   --> ~/.cargo/git/checkouts/stream-body-094892f572609189/4ca8d42/src/body.rs:105:35
    |
105 |             if let Err(err) = io::copy(&mut r, &mut w).await {
    |                                   ^^^^ not found in `io`
    |
help: consider importing one of these items
    |
1   | use core::ptr::copy;
    |
1   | use crate::body::io::async_write::io::copy;
    |
1   | use crate::body::io::async_write::io::sys::ext::net::raw_fd::sys_common::fs::copy;
    |
1   | use crate::body::io::async_write::io::sys::ext::process::process::fs::copy;
    |
      and 5 other candidates

I am not 100% sure why the error did not arise while routerify-websocket was still using tokio 0.2 (probably due to some cargo dependency resolution shenanigans), but it seems to me that stream-body's Cargo.toml should list the features that are used: "rt-core" is required by tokio::spawn and "io-util" is required by tokio::io::copy, both used in body.rs.

Having this PR merged will allow me to continue working on updating routerify-websocket. I may need to follow up with another PR on stream-body (updating to tokio 1.x and hyper 0.14) before being able to push the routerify-websocket update.

[gsserge]

Apologies for the delayed response. I will try to look into the PR soon.

[gsserge]

@ErwanDL maybe we should update to tokio 1 right away?

[ErwanDL]

@gsserge I agree, that PR was just really a temporary fix while I was working on updating to tokio v1. However, I have tried to do the update to tokio v1 on this branch, but I am somewhat stuck at the moment as async-pipe's API has changed, due to tokio's AsyncRead's API changing in v1 (prepare_uninitialized_buffer has disappeared). Given that I'm not too familiar with stream-body's code, I'm having a hard time figuring out the correct fix to accomodate these changes 😕

[threeseed]

@ErwanDL @gsserge

Have pushed a new PR here: #3

Currently using my fork of async-pipe-rs until routerify/async-pipe-rs#10 is merged.

[rousan]

@ErwanDL, @gsserge , I removed the stream-body dependency from routerify-websocket in version 3, as the stream-body uses async-pipe-rs which uses unsafe code, so, for safety and security reasons, we will not use async-pipe-rs and stream-body in Routerify.