chore(Jest): Add babel-jest for proper testing on node 4 & 5

Author: nodkz

package.json

@@ -7,7 +7,6 @@
     "README.md"
   ],
   "main": "lib/index.js",
-  "jsnext:main": "es/index.js",
   "repository": {
     "type": "git",
     "url": "https://github.com/nodkz/graphql-compose-connection.git"
@@ -29,6 +28,7 @@
   "devDependencies": {
     "babel-cli": "^6.24.1",
     "babel-eslint": "^7.2.3",
+    "babel-jest": "^20.0.3",
     "babel-plugin-transform-flow-strip-types": "^6.22.0",
     "babel-plugin-transform-object-rest-spread": "^6.23.0",
     "babel-preset-env": "^1.5.1",