Remove the badge for the dead drone.io service and add Cirrus CI in its place

Author: martin-frbg

README.md

@@ -6,7 +6,8 @@ Travis CI: [![Build Status](https://travis-ci.com/xianyi/OpenBLAS.svg?branch=dev
 
 AppVeyor: [![Build status](https://ci.appveyor.com/api/projects/status/09sohd35n8nkkx64/branch/develop?svg=true)](https://ci.appveyor.com/project/xianyi/openblas/branch/develop)
 
-Drone CI: [![Build Status](https://cloud.drone.io/api/badges/xianyi/OpenBLAS/status.svg?branch=develop)](https://cloud.drone.io/xianyi/OpenBLAS/)
+Cirrus CI: [![Build Status](https://api.cirrus-ci.com/github/xianyi/OpenBLAS.svg?branch=develop)](https://cirrus-ci.com/github/xianyi/OpenBLAS)
+<!-- Drone CI: [![Build Status](https://cloud.drone.io/api/badges/xianyi/OpenBLAS/status.svg?branch=develop)](https://cloud.drone.io/xianyi/OpenBLAS/)-->
 
 [![Build Status](https://dev.azure.com/xianyi/OpenBLAS/_apis/build/status/xianyi.OpenBLAS?branchName=develop)](https://dev.azure.com/xianyi/OpenBLAS/_build/latest?definitionId=1&branchName=develop)