Clickable stack traces in spec runner window

Displays Jasmine failure stack traces with clickable links if a parent Brackets window is available.  Clicking a link jumps to the corresponding source code in the Brackets window.

One thing this unfortunately doesn't do is bring the Brackets window to the front.  CEF still follows the usual browser security model there, blocking JS from doing that.  In the future, we could consider adding a native shell API to support this (at the very least it should be ok to activate a different window within the same app).

@jasonsanjose or @dangoor if you're interested in reviewing...