bugfix for failed multipart parse on empty request

Allow .json .html .xml style urls and also allow these formats to be specified in a "?format=..." query string.

Adding tests for OAuth authentication through django-oauth-plus, a dedicated example project is still missing though

Try to be marginally less awful if we can't reverse resolve the URL for a model.  TODO: Give up on even trying to do such black magic in the first place?

added a `permissions` example with just a per-user-throttle which we may want to expand with some auth examples.

added a `permissions` example with just a per-user-throttle which we may want to expand with some auth examples.

added a `permissions` example with just a per-user-throttle which we may want to expand with some auth examples.

--HG--
rename : djangorestframework/tests/resources.py => djangorestframework/tests/serializer.py

* We now have per-user, per-view and per-resource throttling

* Added a new exxception class as a convenience to detect pointless throttles

* refactored