Fix typo

Fixed use of deprecated Query.aggregates

In Django 1.8 [`Query.aggregates` is replaced by `annotations`](https://docs.djangoproject.com/es/1.9/releases/1.8/#aggregate-methods-and-modules).

Using aggregates currently raises a `RemovedInDjango20Warning`. [Django's source](https://github.com/django/django/blob/1.8/django/db/models/sql/query.py#L192)

Fix blank lines around docstrings

Run JavaScript only when DOM is ready

Add a reference to the dynamic-rest addon

Remove django1.7 from README.md

Remove django1.7 since #296c5676 took django1.7 off the build.

Update Django versions after bugfix release

Fix empty pk detection in HyperlinkRelatedField.get_url

Update Django security releases 1.9.3 and 1.8.10

add rest-framework-generic-relations link to docs

Add `/en` to Heroku guidelines link

[change] using safer calling way of  "@api_view" in docs/tutorial/5-relationships-and-hyperlinked-apis.md

remove comma

This implementation allows detection of empty values that are non-nullable, allowing the field to return None values for such cases

"@api_view" usage error.

Fixes incorrect references to URLPathVersioning

updated tutorial for django 1.9

Docs: Fix repetitive word in the tutorial

Fix typo in relations docs

Create issue and pull request templates

Closes #3952: Remove old django checks from tests and compat

Closes #3937. Support callable as the value of `initial` for any `serializer.Field`

Just like regular Django fields, the example adopted uses a `datetiume.date.today` to
illustrate the functionality.