Adding additional note about the behavior of set permission classes per view as suggest on #3834

QueryParameterVersioning does not use default version

QueryParameterVersioning does not fall back to the value used in the `DEFAULT_VERSION` setting, while other versioning schemes do. This looks like a minor change, and incorporates the `self.default_version` set in the superclass.

I'll sheepishly admit that I edited this inline without running any tests or anything, so please let me know if this needs more work.

Display py.test internal warnings

Regarding #3729

Document how to tweak authtoken.admin.TokenAdmin

python -Werror generates warnings informing that on_delete is a required keyword in Django 2.0

With focus on large user base, but can be extended.

2015 update in __init__.py file

update copyright 2016

Fixed TimeField not handling empty values

PY2: DateField.to_representation can't work with unicode value

Fixes #3786

Added documentation for the third party jsonapi.org package

Fix nested validation error being rendered incorrectly.

Minor fix for dictionary key lookup in settings file

Fixes #3804, avoiding update of Meta.extra_kwargs

Added unit test to cover.

Typo fix in docs/api-guide/relations.md

`slug field` in code snippet was replaced to `slug_field`

Previously an extra list wrapped nested validation errors raised from serializer's validate() methods.
That was inconsistent with the format of validation errors raised by validate_<fieldname> methods.
i.e. these two resulted in *different* behaviour:

    def validate_foo(self):
        raise ValidationError(['bar'])

    def validate(self):
        raise ValidationError({'foo': ['bar']})

don't import authtoken model until needed

Min/MaxValueValidator is no longer transferred from a model's DecimalField

These two tests were previously added in
https://github.com/tomchristie/django-rest-framework/commit/7d79cf35b7be01b175d8c25276a4414e8144a16b
but we have now discovered that there are not actually two separate
cases, there was just a  bug in the code that made it look that way.

This also removes a redundant check to see if `DecimalValidator` was
defined.

Make code block consistent in serialization tutorial

All the other code blocks in the Serialization tutorial can be copied and pasted, but there is one that includes the >>> shell prompt characters. This commit removes those characters, and also makes the output consistent with other code blocks by making it a comment.

Initial fixes #3636 and fixes #3637

Add HTTP status code 451 to status.py