Update README.md

Author: ramittal

README.md

@@ -2,7 +2,7 @@ Authorize.Net PHP SDK
 ======================
 
 [![Build Status]
-(https://travis-ci.org/AuthorizeNet/sdk-php.png?branch=future)]
+(https://travis-ci.org/AuthorizeNet/sdk-php.png?branch=master)]
 (https://travis-ci.org/AuthorizeNet/sdk-php)
 
 ## License