Add 2 methods:

* Resque.delayed? MyJob => Boolean
* Resque.next_delayed_schedule MyJob => timestamp

``` ruby
  # Discover if a job hs been delayed.
  # Examples
  #   Resque.delayed? MyJob
  #   Resque.delayed? MyJob, id: 1
  #   
  # Returns true if the job has been delayed 
  def delayed?(klass, *args)
    search = encode(job_to_hash(klass, args))
    !find_delayed(search).nil?
  end

  # Returns the next timestap for a delayde job
  # Examples
  #   Resque.next_delayed_schedule MyJob
  #   Resque.next_delayed_schedule MyJob, id: 1
  #   
  # Returns the timestamp or nil if does not exists any delayed
  # scheduled for the job 
  def next_delayed_schedule(klass, *args)
    search = encode(job_to_hash(klass, args))
    find_delayed(search)
  end
```