HBOCodeLabs/bluebird — pull request #5 by brendanjc (2014-04-23 22:27:13+00:00)
Title: Callstacks for cancellation and for IE

### CHANGE SUMMARY
* HAD-1335 Promise.cancel() should capture stack immediately
* Adds callstack tracing support for IE 10 by throwing Errors. This is hidden behind a property since it's expensive.
* Adds callstack tracing to cancel() calls, to help track down unhandled rejections that originated from an explicit cancel call.