Catch Twig_Error and show real file

Twig is smart enough to know the template/line where the error occurred.
We can use the loader to find the original path and throw a new
exception.
This is useful to show the 'real' lines from the template in Whoops,
instead of some Twig library file.

Could also abstract the finding of the view in a seperate class, and use that here and in the loader (or combine the path/viewfinder loader)