Add more events to User

There was no way of observing changes to fields like currentlyActive, so add this and add one for lastPresenceTs that will be fired whenever we get a presence event.

lib/sync.js

@@ -1040,7 +1040,10 @@ SyncApi.prototype._onOnline = function() {
 
 function createNewUser(client, userId) {
     var user = new User(userId);
-    reEmit(client, user, ["User.avatarUrl", "User.displayName", "User.presence"]);
+    reEmit(client, user, [
+        "User.avatarUrl", "User.displayName", "User.presence",
+        "User.currentlyActive", "User.lastPresenceTs"
+    ]);
     return user;
 }