syntax errors in tests do not manifest well

[lloyd]

consider this example code:

https://gist.github.com/729297

upon clicking the button there's no visibile output on the page, and I have to go into my debugger to figure out what's happened. It turns out the exception parsing logic in doctest.js doesn't handle this exception well:

https://github.com/ianb/doctestjs/blob/4bced7339ff97834a7561d0e6626deed70018de7/doctest.js#L387-404

This makes debugging tests more difficult than necessary.

(issue experience primarily on chromium/linux, though I can imagine it'd be much different in other environments)

[ianb]

This was because Chrome's .stack attribute is different, so the traceback formatting wasn't working. Should be fixed now.