Update CHANGELOG, Cargo.toml, and docs for 2.0.

src/lib.rs

@@ -12,7 +12,11 @@
 //! the API simple and and keeps dependencies to a minimum. For TLS, ureq uses
 //! [rustls].
 //!
-//! [blocking]: #blocking-i-o-for-simplicity
+//! Version 2.0.0 was released recently and changed some APIs. See the [changelog] for details.
+//!
+//! [blocking]: #blocking-io-for-simplicity
+//! [changelog]: https://github.com/algesten/ureq/blob/master/CHANGELOG.md
+//!
 //!
 //! ## Usage
 //!
@@ -154,7 +158,7 @@
 //!
 //! # Blocking I/O for simplicity
 //!
-//! Rust supports [asynchronous (async) I/O][async], but ureq does not use it. Async I/O
+//! Ureq uses blocking I/O rather than Rust's newer [asynchronous (async) I/O][async]. Async I/O
 //! allows serving many concurrent requests without high costs in memory and OS threads. But
 //! it comes at a cost in complexity. Async programs need to pull in a runtime (usually
 //! [async-std] or [tokio]). They also need async variants of any method that might block, and of