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.
Fix tests
CS Fixes
Fix handling Twig_Error when loading template
Bring into line the name of exception objects with the rest of TwigBridge
Tidy up docblocks
Merge pull request #115 from rcrowe/0.6-errors

Handle Twig_Error correctly so that the file / line is reported correctly.