prepared CHANGELOG for dev

CHANGELOG.md

@@ -4,6 +4,20 @@ All notable changes to the solarium library 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]
+### Added
+
+### Changed
+
+### Deprecated
+
+### Removed
+
+### Fixed
+
+### Security
+
+
 ## [4.0.0]
 ### Added
 - Support "sow" parameter (Split On Whitespace) in select queries