Don't use rc version of graphql-js

Previously we were using a release candidate version of graphql-js
to enable use of the extend type functionality. This is no longer
needed after refactoring the schema augmentation approach, so
using latest stable release version of graphql-js.

package.json

@@ -37,7 +37,7 @@
     "body-parser": "^1.18.3",
     "express": "^4.16.3",
     "graphql-tag": "^2.9.2",
-    "graphql-tools": "^3.0.2",
+    "graphql-tools": "^3.1.1",
     "husky": "^0.14.3",
     "lint-staged": "^7.2.0",
     "node-fetch": "^2.1.2",
@@ -46,7 +46,7 @@
     "prettier": "^1.13.5"
   },
   "dependencies": {
-    "graphql": "14.0.0-rc.2",
+    "graphql": "^0.13.2",
     "lodash": "^4.17.10",
     "neo4j-driver": "^1.6.1"
   },