Django 1.6 friendly imports.

[bahoo]

Borrowed from http://stackoverflow.com/questions/19962736/django-import-error-no-module-named-django-conf-urls-defaults

[bahoo]

This builds on my previous pull request #2 and adds support for specifying an encoder, as mentioned here:

https://github.com/pusher/pusher_client_python#advanced-usage

My specific use-case was Decimals not being serialized properly, which Django's encoder can handle. See: http://stackoverflow.com/a/13257845/412290

Usage:

from django.core.serializers.json import DjangoJSONEncoder
PUSHER_ENCODER = DjangoJSONEncoder