Move to dependency

notebook/lab/package.json

@@ -6,12 +6,12 @@
   "main": "lib/index.js",
   "typings": "lib/index.d.ts",
   "dependencies": {
+    "es6-promise": "^3.1.2",
     "jupyter-js-plugins": "^0.11.8",
     "phosphide": "^0.9.0"
   },
   "devDependencies": {
     "css-loader": "^0.23.1",
-    "es6-promise": "^3.1.2",
     "file-loader": "^0.8.5",
     "json-loader": "^0.5.4",
     "rimraf": "^2.5.0",