not taking advantage of best cleanup command

Author: Billy Clark

Makefile

@@ -1,11 +1,11 @@
-start: 
+start:
 	docker-compose up -d
 
-errors: 
+errors:
 	docker-compose exec hub cat /var/log/apache2/error.log
 	docker-compose exec idp1 cat /var/log/apache2/error.log
 	docker-compose exec idp2 cat /var/log/apache2/error.log
 
 clean:
 	docker-compose kill
-	docker-compose rm -f
+	docker system prune -f