UUID support in URLs

Thanks for the good extension that helps a lot!

I have problems using it with Flask-UUID extension and URLs that have UUIDs inside. Is it possible to fix this? Providing stack trace below:

File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1997, in __call__
return self.wsgi_app(environ, start_response)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1985, in wsgi_app
response = self.handle_exception(e)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1540, in handle_exception
reraise(exc_type, exc_value, tb)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1982, in wsgi_app
response = self.full_dispatch_request()
File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1615, in full_dispatch_request
return self.finalize_request(rv)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1632, in finalize_request
response = self.process_response(response)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask/app.py", line 1856, in process_response
response = handler(response)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask_debugtoolbar/__init__.py", line 223, in process_response
toolbar_html = toolbar.render_toolbar()
File "..prog_path/e_venv/lib/python2.7/site-packages/flask_debugtoolbar/toolbar.py", line 46, in render_toolbar
return template.render(**context)
File "..prog_path/e_venv/lib/python2.7/site-packages/jinja2/environment.py", line 1008, in render
return self.environment.handle_exception(exc_info, True)
File "..prog_path/e_venv/lib/python2.7/site-packages/jinja2/environment.py", line 780, in handle_exception
reraise(exc_type, exc_value, tb)
File "..prog_path/e_venv/lib/python2.7/site-packages/flask_debugtoolbar/templates/base.html", line 50, in top-level template code
{{ panel.content()|safe }}
File "..prog_path/e_venv/lib/python2.7/site-packages/flask_debugtoolbar/panels/sqlalchemy.py", line 122, in content
'signed_query': dump_query(query.statement, query.parameters),
File "..prog_path/e_venv/lib/python2.7/site-packages/flask_debugtoolbar/panels/sqlalchemy.py", line 34, in dump_query
return query_signer().dumps([statement, params])
File "..prog_path/e_venv/lib/python2.7/site-packages/itsdangerous.py", line 565, in dumps
payload = want_bytes(self.dump_payload(obj))
File "..prog_path/e_venv/lib/python2.7/site-packages/itsdangerous.py", line 847, in dump_payload
json = super(URLSafeSerializerMixin, self).dump_payload(obj)
File "..prog_path/e_venv/lib/python2.7/site-packages/itsdangerous.py", line 550, in dump_payload
return want_bytes(self.serializer.dumps(obj))
File "..prog_path/e_venv/lib/python2.7/site-packages/itsdangerous.py", line 51, in dumps
return json.dumps(obj, separators=(',', ':'))
File "/usr/lib64/python2.7/json/__init__.py", line 251, in dumps
sort_keys=sort_keys, **kw).encode(obj)
File "/usr/lib64/python2.7/json/encoder.py", line 207, in encode
chunks = self.iterencode(o, _one_shot=True)
File "/usr/lib64/python2.7/json/encoder.py", line 270, in iterencode
return _iterencode(o, 0)
UnicodeDecodeError: 'utf8' codec can't decode byte 0xe8 in position 0: invalid continuation byte

Start at flask_debugtoolbar/panels/sqlalchemy.py, especially dump_query and query_signer(), using the provided UnicodeDecodeError as the first failure to reproduce. Look for existing tests covering SQLAlchemy panel rendering and add coverage for the UUID-related case; done means the toolbar renders without this encoding error.