Merge pull request #1468 from Unity-Technologies/release-v0.6-tick-communication

Ticked the communication version to API-6

UnitySDK/Assets/ML-Agents/Scripts/Academy.cs

         [SerializeField] 
         public BroadcastHub broadcastHub = new BroadcastHub();
         
-        private const string kApiVersion = "API-5";
+        private const string kApiVersion = "API-6";
 
         // Fields provided in the Inspector
 

ml-agents/mlagents/envs/environment.py

         atexit.register(self._close)
         self.port = base_port + worker_id
         self._buffer_size = 12000
-        self._version_ = "API-5"
+        self._version_ = "API-6"
         self._loaded = False  # If true, this means the environment was successfully loaded
         self.proc1 = None  # The process that is started. If None, no process was started
         self.communicator = self.get_communicator(worker_id, base_port)