mark v0.4.0 for release
[package]
name = "rtcp"
-version = "0.3.4"
+version = "0.4.0"
authors = ["Rain Liu <yliu@webrtc.rs>", "Michael Uti <utimichael9@gmail.com>"]
edition = "2018"
description = "A pure Rust implementation of RTCP"
