chore(package): update ioredis to version 4.0.0

Author: greenkeeper[bot]

package.json

@@ -30,7 +30,7 @@
   "devDependencies": {
     "chai": "^4.0.1",
     "codeclimate-test-reporter": "^0.4.0",
-    "ioredis": "^3.0.0",
+    "ioredis": "^4.0.0",
     "istanbul": "^0.4.3",
     "safe-stable-stringify": "^1.0.0",
     "mocha": "^6.0.0",