updated CHANGES.md

Author: ryanflorence

CHANGES.md

@@ -1,14 +1,19 @@
-## [HEAD] \(v2.1.0\)
+## [HEAD]
 > Unreleased
 
+[HEAD]: https://github.com/reactjs/react-router/compare/latest...HEAD
+
+## [v2.1.0]
+> April 11, 2016
+
 - **Feature:** Add support for `onChange` hook on routes ([#3108])
 - **Minor:** Include full warning messages in non-minified UMD build ([#3213])
 - **Minor:** Speed up path matching ([#3217])
 
-[HEAD]: https://github.com/reactjs/react-router/compare/latest...HEAD
 [#3108]: https://github.com/reactjs/react-router/pull/3108
 [#3213]: https://github.com/reactjs/react-router/pull/3213
 [#3217]: https://github.com/reactjs/react-router/pull/3217
+[v2.1.0]: https://github.com/reactjs/react-router/compare/v2.0.1...v2.1.0
 
 ## [v2.0.1]
 > March 9, 2016