[changelog] added client header

Author: VinayBhalerao

CHANGELOG.md

@@ -3,8 +3,11 @@ All notable changes to this project will be documented in this file.
 
 ## Unreleased
 
+### Added
+- Added client header ```X-3scale-User-Agent: plugin-php-v{version-number} 
+
 ### Changed
-- Allow custom host and port configurable for 3scale On premise SAAS platform [PR #16](https://github.com/3scale/3scale_ws_api_for_php/.)  Note: For example, the signature is changed from ```$url = "http://" . $this->getHost() . "/transactions/authorize.xml"``` to ```$url = $this->getHost() . "/transactions/oauth_authorize.xml";``` for endpoints
+- Allow custom host and port configurable for 3scale On premise SAAS platform [PR #16](https://github.com/3scale/3scale_ws_api_for_php/pull/16)  Note: For example, the signature is changed from ```$url = "http://" . $this->getHost() . "/transactions/authorize.xml"``` to ```$url = $this->getHost() . "/transactions/oauth_authorize.xml";``` for endpoints
 
 ##[2.7.0] - 2017-02-16
 ### Added