:args option for run_callbacks

Patch attached, here's the branch

#   * +:args+ - Pass the provided arguments array to each callback method or proc.
#     Arguments that exeed the arity of the callback method/proc will be silently
#     discarded rather then generate a warning. String callbacks cannot receieve
#     arguments. (default: +[]+ i.e. no arguments will be passed)

Example:

  def investigate(suspect)
    run_callback :before_investigation, :args=>[suspect]
    # ...
    run_callback :after_investigation, :args=>[suspect]
  end
  
  before_investigation :plant_evidence
  after_investigation :testify_in_court

  def plant_evidence(suspect)
    suspect.plant(INCRIMINATING_STUFF)
  end
  
  def testify_in_court
    # ... 
    # Note i don't need to expect the (suspect) arg if I'm not going to use it
  end
end