add build status button

Author: inhere

README.md

@@ -3,6 +3,7 @@
 [![License](https://img.shields.io/packagist/l/inhere/sroute.svg?style=flat-square)](LICENSE)
 [![Php Version](https://img.shields.io/badge/php-%3E=7.0-brightgreen.svg?maxAge=2592000)](https://packagist.org/packages/inhere/sroute)
 [![Latest Stable Version](http://img.shields.io/packagist/v/inhere/sroute.svg)](https://packagist.org/packages/inhere/sroute)
+[![Build Status](https://travis-ci.org/inhere/php-srouter.svg?branch=master)](https://travis-ci.org/inhere/php-srouter)
 
 非常快速且轻量的请求匹配路由器。