readme: changelog bump for 2.0 - breaking change about config.

Author: paulirish

README.md

@@ -198,7 +198,7 @@ Copyright Jason McCreary & Paul Irish. Licensed under MIT.
 
 ## Changelog
 
-- **2017-12-01** - 2.0 shipped
+- **2017-12-01** - 2.0 shipped. Breaking change: [Gitlab configuration](https://github.com/paulirish/git-open#configuration) handled differently.
 - **2017-12-01** - Configuration for custom remote added
 - **2017-11-30** - Support for VSTS Added
 - **2017-10-31** - `--issue` and `-h` added