4.0.0

This release allows `HttpClient` to be used as a dynamic Trait object.

- `HttpClient`: removed `Clone` bounds.
- `HttpClient`: removed `Error` type.

Author: Fishrock123

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "http-client"
-version = "3.0.0"
+version = "4.0.0"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/http-rs/http-client"
 documentation = "https://docs.rs/http-client"