added cookiecutter-django-dokku to README.rst
added cookiecutter-django-dokku to README.rst

hackebrot/cookiecutter,audreyr/cookiecutter,pjbull/cookiecutter,hackebrot/cookiecutter,michaeljoseph/cookiecutter,luzfcb/cookiecutter,pjbull/cookiecutter,michaeljoseph/cookiecutter,luzfcb/cookiecutter,audreyr/cookiecutter