[TORQUE-790] Scheduled message delivery

Fix for https://issues.jboss.org/browse/TORQUE-790, example usage:

```ruby
# Send a message 2 sec later
queue.publish "wassup", :scheduled => Time.now.to_i * 1000 + 2 * 1000

# Send a message 5 sec later and receive the response
queue.publish_and_receive "wassup", :timeout => 1000, :scheduled => Time.now.to_i * 1000 + 5 * 1000
```