fix(package): update sequelize to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -18,7 +18,7 @@
   "dependencies": {
     "bluebird": "^3.3.4",
     "lodash": "^4.6.1",
-    "sequelize": "^3.20.0"
+    "sequelize": "^4.0.0"
   },
   "devDependencies": {
     "babel-cli": "^6.2.0",