Add more information to Changelog in README.

Add information about 1.7.1, all 1.6.x releases, and all 1.5.x bugfix
releases.

Fix #105.

Add license to setup.py

This makes it easy to see the license at-a-glance from services such as pyup.io

Drop support for Django < 1.8 and related cleanups

Added DummySerializer to use when values to get/set are already seria…

The need arose when I wanted to cache serialized output of django-tastypie list endpoints. The output was json already, so it makes no sense to re-serialize it with pickle parser or json parser.

Use default timeout in set_many.

get_many and set_many should work the same way as in other cache backends

Instead of raising an exception it should just return without doing anything.

Instead of raising an exception it should return an empty dict

This is the same behaviour that the default Django cache backends have.