Add CHANGELOG

Author: jszwedko

CHANGELOG.md

@@ -0,0 +1,17 @@
+# Change Log
+
+**ATTN**: This project uses [semantic versioning](http://semver.org/).
+
+## [Unreleased]
+
+## 0.2.0 - 2016-11-19
+Bug fixes:
+* Only query for the current project once (remove duplicate warning messages)
+* Friendlier error messages when CircleCI token is not set
+
+Features:
+* `list-env-vars` command added
+
+## 0.1.0 - 2016-01-22
+### Added
+- Initial implementation.