indicate a successful removal of a machine

Signed-off-by: Luke Roberts <luke@speak.io>

commands.go

@@ -653,6 +653,8 @@ func cmdRm(c *cli.Context) {
 	}
 	if isError {
 		log.Fatal("There was an error removing a machine. To force remove it, pass the -f option. Warning: this might leave it running on the provider.")
+	} else {
+		log.Print("The machine was successfully removed")
 	}
 }