I added optional field messages which allows to handle specific action not before given timestamp. Such functionality
allows to schedule some actions in the future, which could be nice feature.

If valid_at parameter is not given ap4r process message immediately, which is old behaviour.

example usage:
ap4r.async_to({:action => :test}, {:id => 123}, {:valid_at => Time.now.to_i + 3, :priority => 1})

Date: 2008-01-09 13:58
Sender: shunichi shinohara

Nice extention!
The Selector is one of useful features of reliable-msg, so I
want to take advantage of that.

I am anxious about the case that:
  large number of messages in a queue, and
  those are "not-valid-yet".
For example, messages those should be processed at midnight.

I parhaps should consider some kind of scheduling.