title: Terminate Conversation with Pending Callbacks
body: <p>Is there any way or method to abruptly stop the bot's dialog/conversation when it typed 'stop' together with any pending callbacks within a waterfall step? </p>
  
  <p>There is handling for 'stop' built-in, but it just stops the waterfall from proceeding. </p>
  
  <p>Given the scenario of a waterfall dialog, <code>stepA</code> → <code>stepB</code> → <code>stepC</code>. The dialog starts at <code>stepA</code>, proceeds to <code>stepB</code> which calls a HTTP request with a callback, before the request finished and before proceeding to <code>stepC</code>, user types <code>stop</code>, ends the dialog, however, within <code>stepB</code>, there is a code on the callback <code>session.send(output)</code>. This will get sent regardless if I already stopped the the dialog.</p>
  
  <p>Note: I'm still using V1. Seeing V3 has <code>endConversation</code>, it doesn't still work as expected.</p>