chore(package): update readable-stream to version 2.3.1

Author: greenkeeper[bot]

package.json

@@ -28,6 +28,6 @@
     "nyc": "^11.0.2"
   },
   "dependencies": {
-    "readable-stream": "^2.0.6"
+    "readable-stream": "^2.3.1"
   }
 }