Update Changelog (#16)

Changelog is updated with the latest changes to the program.

Signed-off-by: Elis Lulja <elulja@cisco.com>

CHANGELOG.md

@@ -5,27 +5,32 @@ All notable changes to this project will be documented in this file.
 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).
 
+## [0.4.0] (2021-01-26)
+
+### Added
+
+- Ability to provide CLI flags from a configuration file
+
+### Fixed
+
+- Better validation for polling interval, which now takes care of negative
+values.
+
 ## [0.3.0] (2020-09-24)
 
 ### Added
 
 - This Changelog
-
 - Readme: `Go Get` section
-
 - Readme: `Clone The Project` section
-
 - Readme: `Run as a Docker Container` section
-
 - Readme: `Metadata Key` section
-
 - Version command: `cnwan-reader version [--short|-s]`
 
 ### Changed
 
 - Readme has been improved drastically with many sections being rewritten
 in an effort to make it more understandable.
-
 - `--metadata-key` is moved to `service directory`, as it would trigger an
 error in `version`.
 
@@ -46,13 +51,10 @@ waiting for adaptor to replying is fixed.
 ### Changed
 
 - `--metadata-key` is now required
-
 - `--credentials` is now moved under `servicedirectory` command and changed to
 `--service-account` for better understing
-
 - `--region` and `--project` are now marked as required in the framework and
 thus not checked by the project anymore
-
 - Readme: improve description on commands.
 
 ## [0.1.1] (2020-08-13)