title: trap when.js unhandled rejections
body: <p>I'd like to trap when.js unhandled rejections so that I can log them. To accomplish this I've overriden console.warn(), however that can log stuff other than when.js which I'm not interested in.</p>
  
  <p>ref: <a href="https://github.com/cujojs/when/blob/master/docs/api.md#debugging-promises">https://github.com/cujojs/when/blob/master/docs/api.md#debugging-promises</a></p>
  
  <p>I am using prettymonitor with when.js <a href="https://github.com/AriaMinaei/pretty-monitor">https://github.com/AriaMinaei/pretty-monitor</a></p>