chore: bump version to 0.4.0 and update changelog

CHANGELOG.md

@@ -5,6 +5,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+
+## [v0.4.0] - 2021-04-23
 ### Changed
 - update dependencies, including stable tokio this time.
 - migrate error handling to anyhow

Cargo.lock

@@ -447,7 +447,7 @@ dependencies = [
 
 [[package]]
 name = "peshming"
-version = "0.3.0"
+version = "0.4.0"
 dependencies = [
  "anyhow",
  "async-anyhow-logger",

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "peshming"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["Jan Christian Grünhage <jan.christian@gruenhage.xyz>"]
 edition = "2018"
 description = "Pings configured hosts in a configurable intervals and exposes metrics for prometheus."