update qs to 6.4.0

Author: BrandonCopley

package.json

@@ -26,7 +26,7 @@
     "faye-websocket": "~0.10.0",
     "livereload-js": "^2.2.2",
     "object-assign": "^4.1.0",
-    "qs": "^6.2.0"
+    "qs": "^6.4.0"
   },
   "devDependencies": {
     "babel-cli": "^6.9.0",