Update changelog with 3.1.4

Author: genail

CHANGELOG.md

@@ -4,7 +4,7 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
-## [Unreleased]
+## [3.1.4]
 ### Fixed
 - HTTP downloader resumes the download on error
 - Fix TorrentDownloader progress reporting for big files