added change log

Author: Puneet Khushwani

CHANGELOG.md

@@ -0,0 +1,10 @@
+[OST PHP SDK v1.1.0](https://github.com/OpenSTFoundation/ost-sdk-php/tree/v1.1.0) July 2 2018
+---
+
+* Added user balances module to V1 API's
+* Added transaction ledger module to V1 API's
+
+[OST PHP SDK v1.0.0](https://github.com/OpenSTFoundation/ost-sdk-php/tree/v1.0.0) May 30 2018
+---
+Initial release of the official OST PHP SDK<br />
+This release has the OST API interaction layer implementation.