cleaned up celery.platforms.PIDFile

Bumped version to 2.1.0rc1

New version requirement carrot>=0.10.6

Fixed typos/wording in Changelog

Bumped version to 2.0.3 and updated Changelog

Changelog: Fixed rst indentation issue

Fixed typos in Changelog

Removes django-picklefield from contrib/requirements/default.txt

Forgot to render README

Added internal reference autodoc for celery.backends.cache