Add stacktrace to ParseError

Fixes #854. Also clean up the parse error test a little, while adding a .stack check.
> And since we support IE >= 8, tests need to run in IE >= 8.

Oh. Welp. Guess we should just not test for it, then. Still, it would be good to figure out the IE10-11 thing.

It seems like we can't get the stack just from a `new Error()`, and http://msdn.microsoft.com/en-us/library/ie/hh699850(v=vs.94).aspx actually says this now that I look again: 

> The stack property is set to undefined when the error is constructed, and gets the trace information when the error is raised. If an error is raised multiple times, the stack property is updated each time the error is raised.

I guess we have to actually throw an error and grab the stack off of it.