Added version 2.2.0 to the changelog

Author: mmallis87

CHANGELOG.md

@@ -7,6 +7,10 @@ See [DocuSign Support Center](https://support.docusign.com/en/releasenotes/) for
 ### Changed
 - Updated the package with the latest API monthly release.
 
+## [2.2.0] - 2017-06-17
+### Added
+- Added support for DocuSign OAuth
+
 ## [2.1.0] - 2017-03-09
 ### Added
 - TravisCI automatic tests.