docs: Update README

README.md

@@ -2,7 +2,7 @@
 
 [![Documentation][godoc-img]][godoc-url]
 ![License][license-img]
-[![Build Status][travis-img]][travis-url]
+[![Build Status][circle-img]][circle-url]
 [![Go Report Card][goreport-img]][goreport-url]
 
 *Dead simple rate limit middleware for Go.*
@@ -167,7 +167,7 @@ Don't hesitate ;)
 [godoc-url]: https://godoc.org/github.com/ulule/limiter
 [godoc-img]: https://godoc.org/github.com/ulule/limiter?status.svg
 [license-img]: https://img.shields.io/badge/license-MIT-blue.svg
-[travis-url]: https://travis-ci.org/ulule/limiter
-[travis-img]: https://travis-ci.org/ulule/limiter.svg?branch=master
 [goreport-url]: https://goreportcard.com/report/github.com/ulule/limiter
 [goreport-img]: https://goreportcard.com/badge/github.com/ulule/limiter
+[circle-url]: https://circleci.com/gh/ulule/limiter/tree/master
+[circle-img]: https://circleci.com/gh/ulule/limiter.svg?style=shield&circle-token=baf62ec320dd871b3a4a7e67fa99530fbc877c99