chore(node): specify requires node < 10

Author: olets

package.json

@@ -4,7 +4,7 @@
   "description": "A full featured configurable asset pipeline and static site builder",
   "license": "MIT",
   "engines": {
-    "node": ">=6.11.1",
+    "node": ">=6.11.1 <10",
     "npm": ">=3.10.3"
   },
   "main": "gulpfile.js/index.js",