Require Node.js >= 4.8.0 for the shell option of child_process.spawn

Author: sun-zheng-an

package.json

@@ -39,6 +39,6 @@
     "through2": "^2.0.3"
   },
   "engines": {
-    "node": ">=4"
+    "node": ">=4.8.0"
   }
 }