Udpated aicrowd.json token

aicrowd.json

 {
-  "challenge_id": "aicrowd_flatland_challenge_2019",
-  "grader_id": "aicrowd_flatland_challenge_2019",
-  "authors": ["mohanty"],
-  "description": "Random Agent for Flatland Challenge.",
-  "debug" : true
+  "challenge_id": "neurips-2020-flatland-challenge",
+  "grader_id": "neurips-2020-flatland-challenge",
+  "description": "Optional description of your agent",
+  "debug": true
 }