add useful minimize options

Author: sokra

lib/processCss.js

@@ -159,7 +159,10 @@ module.exports = function processCss(inputSource, inputMap, options) {
 	]);
 
 	if(minimize) {
-		pipeline.use(cssnano());
+		pipeline.use(cssnano({
+			zindex: false,
+			urls: false
+		}));
 	}
 
 	var result = pipeline.process(inputSource, {