This fixes a redirection loop causing an authenticated user which is
*not* staff accessing /admin to be loop-redirected between
/admin -> /admin/login -> /accounts/login
Also include some hideous basic page to show a message. This should not
be a problem; a non-admin user accessing /admin deserves hurting their
eyes.
- Update django-allauth-cas to the last version.
- Add docs (README, example/README).
- Add tests for Clipper provider.
- Add tests to check templates do not contain syntax error.
- Add the last missing templates to override all allauth's displayable
templates.
- Improve stylesheets.
