title: Google apps - Trigger script when responseStatus change
body: <p>I would like to run a script each time the responStatus of an event is modified by an attendee.
  By default when an attendee receive an invitation by email the status is "needsAction". And wether he accepts, decline, the responseStatus change to "accepted" or "declined".</p>
  
  <p>I want to create a script which send a custom email, and trigger each time the status is changed by the attendees.</p>
  
  <p>Anyone ?</p>