Restore changelog for continued dev

Author: wjohnstondrip

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+[master]: https://github.com/DripEmail/drip-ruby/compare/v3.0.0...HEAD
+
+- Your contribution here!
+
 ## [3.1.0] - 2018-06-05
 
 [3.1.0]: https://github.com/DripEmail/drip-ruby/compare/v3.0.0...v3.1.0