v0.99.9

This patch upgrades our futures-rs version, allowing us to build on the 1.39
beta. Additionally we've introduced map and for_each to Stream. And we've
added about a dozen new FromStream implementations for std types, bringing
us up to par with std's FromIterator implementations.

And finally we've added a new "unstable" task::blocking function which can be
used to convert blocking code into async code using a threadpool. We've been
using this internally for a while now to async-std to power our fs and
net::SocketAddr implementations. With this patch userland code now finally has
access to this too.

Example

Create a stream of tuples, and collect into a hashmap

let a = stream::once(1u8);
let b = stream::once(0u8);

let s = a.zip(b);

let map: HashMap<u8, u8> = s.collect().await;
assert_eq!(map.get(&1), Some(&0u8));

Spawn a blocking task on a dedicated threadpool

task::blocking(async {
    println!("long-running task here");
}).await;

Added

• Added stream::Stream::map
• Added stream::Stream::for_each
• Added stream::Stream::try_for_each
• Added task::blocking as "unstable"
• Added FromStream for all std::{option, collections, result, string, sync} types.
• Added the path submodule as "unstable".

Changed

• Updated futures-preview to 0.3.0-alpha.19, allowing us to build on rustc 1.39.0-beta.
• As a consequence of this upgrade, all of our concrete stream implementations
  now make use of Stream::size_hint to optimize internal allocations.
• We now use GitHub Actions through actions-rs,
  in addition to Travis CI. We intend to fully switch in the near future.
• Fixed a bug introduced in 0.99.6 where Unix Domain Listeners would sometimes become unresponsive.
• Updated our sync::Barrier docs to match std.
• Updated our stream::FromStream docs to match std's FromIterator.