added changelog

Author: Puneet Khushwani

CHANGELOG.md

@@ -0,0 +1,11 @@
+[OST Ruby SDK v1.0.0](https://github.com/OpenSTFoundation/ost-sdk-ruby/tree/v1.0.0) May 17 2018
+---
+
+* Added support for interacting with V1 API along with V0 
+* [README.md](README.md) has API V1 usage instructions
+* [README_V0.md](README.md) has API V0 usage instructions  
+
+[OST Ruby SDK v0.9.2](https://github.com/OpenSTFoundation/ost-sdk-ruby/tree/v0.9.2) March 15 2018
+---
+Initial release of the official OST Ruby SDK<br />
+This release has the OST API V0 interaction layer implementation.