Update Changelog for release of version 2.6.0

Author: LaunchDarklyCI

CHANGELOG.md

@@ -3,6 +3,14 @@
 
 All notable changes to the LaunchDarkly Java SDK will be documented in this file. This project adheres to [Semantic Versioning](http://semver.org).
 
+## [2.6.0] - 2018-02-12
+## Added
+- Adds support for a future LaunchDarkly feature, coming soon: semantic version user attributes.
+
+## Changed
+- It is now possible to compute rollouts based on an integer attribute of a user, not just a string attribute.
+
+
 ## [2.5.1] - 2018-01-31
 
 ## Changed