include missing dep

package.json

@@ -54,6 +54,7 @@
     "cross-spawn": "^4.0.0",
     "de-indent": "^1.0.2",
     "entities": "^1.1.1",
+    "es6-promise": "^3.2.1",
     "eslint": "^3.4.0",
     "eslint-config-vue": "^1.0.3",
     "eslint-loader": "^1.3.0",