[chore] Bump engine.io to version 2.0.2 (#2864)

Includes the following (from engine.io changelog):

* [fix] Initialize the WebSocket server in the Server constructor (#476)
* [chore] Bump ws to version 1.1.2 (vulnerability fix) (#480)

package.json

@@ -25,7 +25,7 @@
   },
   "dependencies": {
     "debug": "2.3.3",
-    "engine.io": "2.0.0",
+    "engine.io": "2.0.2",
     "has-binary": "0.1.7",
     "object-assign": "4.1.0",
     "socket.io-adapter": "0.5.0",