update README

README.md

@@ -1,6 +1,6 @@
 # frp
 
-[![Build Status](https://travis-ci.org/fatedier/frp.svg?branch=master)](https://travis-ci.org/fatedier/frp)
+[![Build Status](https://circleci.com/gh/fatedier/frp.svg?style=shield)](https://circleci.com/gh/fatedier/frp)
 [![GitHub release](https://img.shields.io/github/tag/fatedier/frp.svg?label=release)](https://github.com/fatedier/frp/releases)
 
 [README](README.md) | [中文文档](README_zh.md)