Added build icon

Author: babenkoivan

README.md

@@ -6,6 +6,7 @@
 
 [![Packagist](https://img.shields.io/packagist/v/babenkoivan/scout-elasticsearch-driver.svg)](https://packagist.org/packages/babenkoivan/scout-elasticsearch-driver)
 [![Packagist](https://img.shields.io/packagist/dt/babenkoivan/scout-elasticsearch-driver.svg)](https://packagist.org/packages/babenkoivan/scout-elasticsearch-driver)
+[![Build Status](https://travis-ci.com/babenkoivan/scout-elasticsearch-driver.svg?branch=master)](https://travis-ci.com/babenkoivan/scout-elasticsearch-driver)
 [![Gitter](https://img.shields.io/gitter/room/nwjs/nw.js.svg)](https://gitter.im/scout-elasticsearch-driver/Lobby)
 [![Donate](https://img.shields.io/badge/donate-PayPal-blue.svg)](https://www.paypal.me/ivanbabenko)