Added back stylus utils

Signed-off-by: Avior <florian.bouillon@delta-wings.net>

src/dzeio/stylusUtils.js

@@ -0,0 +1,11 @@
+
+// See https://github.com/stylus/stylus/issues/1872#issuecomment-86553717
+var stylus = require('stylus');
+
+module.exports = function() {
+	return function(style) {
+		style.define('file-exists', function(path) {
+		return !!stylus.utils.lookup(path.string, this.paths);
+		});
+	};
+};