Update README.md to only display build status for master

Author: dynamiccast

README.md

@@ -1,6 +1,6 @@
 # Sails-JSON-API-Blueprints
 
-[![NPM version](https://badge.fury.io/js/sails-json-api-blueprints.svg)](http://badge.fury.io/js/sails-json-api-blueprints)    [![Build Status](https://travis-ci.org/dynamiccast/sails-json-api-blueprints.svg)](https://travis-ci.org/dynamiccast/sails-json-api-blueprints)
+[![NPM version](https://badge.fury.io/js/sails-json-api-blueprints.svg)](http://badge.fury.io/js/sails-json-api-blueprints)   [![Build Status](https://travis-ci.org/dynamiccast/sails-json-api-blueprints.svg?branch=master)](https://travis-ci.org/dynamiccast/sails-json-api-blueprints)
 
 Sails hook to automatically turn a Sails.js API into a [JSON API](http://jsonapi.org/) compatible interface.