readme: Replace CI badges

README.md

@@ -4,8 +4,7 @@
 <h3 align="center">Every Site on HTTPS <!-- Serve Confidently --></h3>
 <p align="center">Caddy is a general-purpose HTTP/2 web server that serves HTTPS by default.</p>
 <p align="center">
-	<a href="https://travis-ci.org/mholt/caddy"><img src="https://img.shields.io/travis/mholt/caddy.svg?label=linux+build"></a>
-	<a href="https://ci.appveyor.com/project/mholt/caddy"><img src="https://img.shields.io/appveyor/ci/mholt/caddy.svg?label=windows+build"></a>
+	<a href="https://dev.azure.com/mholt-dev/Caddy/_build?definitionId=1"><img src="https://img.shields.io/azure-devops/build/mholt-dev/afec6074-9842-457f-98cf-69df6adbbf2e/1/master.svg?label=cross-platform%20tests"></a>
 	<a href="https://godoc.org/github.com/mholt/caddy"><img src="https://img.shields.io/badge/godoc-reference-blue.svg"></a>
 	<a href="https://goreportcard.com/report/mholt/caddy"><img src="https://goreportcard.com/badge/github.com/mholt/caddy"></a>
 	<br>