Update docs on object-level permissions.

Closes #801.
Typo
Changed DepthTest to have depth=2
Changed definition of NestedModelSerializer to correct depth handling
Merge pull request #802 from chenjyw/master

Fix nesting issue with depth >=2
Added @chenjyw for depth bugfix #802.  Thanks!
Catch ImproperlyConfigured exception in compat.py (fixes #803)
Merge pull request #804 from dbrgn/iss803

Catch ImproperlyConfigured exception in compat.py
Example and spelling fixes. Change "browseable" to "browsable" for consistency.
Merge pull request #805 from vshih/master

Example and spelling fixes.
Merge branch 'master' of git://github.com/tomchristie/django-rest-framework