feat(Teleport): add events to teleport

Adds 'Teleporting' and 'Teleported' events which pass along
DestinationMarkerEventArgs to any interested parties.

Assets/SteamVR_Unity_Toolkit/Scripts/VRTK_BasicTeleport.cs

@@ -14,6 +14,8 @@ namespace VRTK
     using UnityEngine;
     using System.Collections;
 
+    public delegate void TeleportEventHandler(object sender, DestinationMarkerEventArgs e);
+
     public class VRTK_BasicTeleport : MonoBehaviour
     {
         public float blinkTransitionSpeed = 0.6f;
@@ -22,6 +24,9 @@ public class VRTK_BasicTeleport : MonoBehaviour
         public bool headsetPositionCompensation = true;
         public string ignoreTargetWithTagOrClass;
 
+        public event TeleportEventHandler Teleporting;
+        public event TeleportEventHandler Teleported;
+
         protected Transform eyeCamera;
         protected bool adjustYForTerrain = false;
         protected bool enableTeleport = true;
@@ -31,6 +36,16 @@ public class VRTK_BasicTeleport : MonoBehaviour
         private float maxBlinkTransitionSpeed = 1.5f;
         private float maxBlinkDistance = 33f;
 
+        private void OnTeleporting(DestinationMarkerEventArgs e) {
+            if (Teleporting != null)
+                Teleporting(this, e);
+        }
+
+        private void OnTeleported(DestinationMarkerEventArgs e) {
+            if (Teleported != null)
+                Teleported(this, e);
+        }
+
         public void InitDestinationSetListener(GameObject markerMaker)
         {
             if (markerMaker)
@@ -74,10 +89,12 @@ protected virtual void DoTeleport(object sender, DestinationMarkerEventArgs e)
         {
             if (enableTeleport && ValidLocation(e.target) && e.enableTeleport)
             {
+                OnTeleporting(e);
                 Vector3 newPosition = GetNewPosition(e.destinationPosition, e.target);
                 CalculateBlinkDelay(blinkTransitionSpeed, newPosition);
                 Blink(blinkTransitionSpeed);
                 SetNewPosition(newPosition, e.target);
+                OnTeleported(e);
             }
         }