Django-scim2

------
- Improve PATCH paths passed into handlers.

If you have custom handlers for patch calls defined in your adapters file
(eg. def handle_add(path, value, operation): ...) then you will need to
update your handlers to accept a 3-tuple in place of the current string held
by path. A quick fix for this is to add the following line to the beginning of
each handler:

path, subattr, uri = path

Thanks for your patience as we migrate to a better system for handling PATCH
paths.

------
- Include schemas in packaged version. Thanks stefanfoulis!
- Fix 21. Store and return externalId
- Fix 22. Handle more complicated PATH calls
Please note: the parse_path_and_value method on the SCIMMixin adapter
changed signature. Please update your code accordingly.

------
- Add logic to add extra SQL to filters

------
- Replace PyPlus with scim2-filter-parser for better filter parsing
- Move tests out of django_scim app folder to root of repo

------
- Return better errors for malformed or unsupported JSON bodies

------
- Create a NotImplementedError for SCIM
- Refactor FilterTransformers