Add stacktrace to ParseError

Fixes #854. Also clean up the parse error test a little, while adding a .stack check.
Without that it's:
```
Expected: 	
"Illegal closing tag at line 1 character 7:
<div> </!!div>
      ^----"
Result: 	
undefined
```
If the check was in ```catch```, there is no reason to remove that "no error thrown" message, is there? But again, it doesn't really matter how you do this, it just needs to work...