Update README.md

Author: Quentin Perez

README.md

@@ -34,8 +34,9 @@ $ go get -u github.com/scaleway/docker-machine-driver-scaleway
 You can find sources and pre-compiled binaries [here](https://github.com/scaleway/docker-machine-driver-scaleway/releases/latest)
 
 ```shell
-# Download the binary
-$ curl -sL https://github.com/scaleway/docker-machine-driver-scaleway/releases/download/v1.2.1/docker-machine-driver-scaleway_1.2.1_darwin_amd64.zip | tar xf -
+# Download the binary (this example downloads the binary for darwin amd64)
+$ curl -sL https://github.com/scaleway/docker-machine-driver-scaleway/releases/download/v1.2.1/docker-machine-driver-scaleway_1.2.1_darwin_amd64.zip -O
+$ unzip docker-machine-driver-scaleway_1.2.1_darwin_amd64.zip
 
 # Make it executable and copy the binary in a directory accessible with your $PATH
 $ chmod +x docker-machine-driver-scaleway_1.2.1_darwin_amd64/docker-machine-driver-scaleway