chore(engines): specify supported node.js versions

package.json

@@ -59,5 +59,8 @@
     "source-map-support": "^0.4.11",
     "tmp": "0.0.31",
     "yargs": "^7.0.1"
+  },
+  "engines": {
+    "node": ">=5.10.0"
   }
 }