Fix broken import

Django 1.6 does not have a module named `django.conf.urls.defaults`. Remove
references to this module and insert more appropriate imports.

Also, reformat some text for the sake of readability.
Use `json`, not `django.utils.simplejson`.

The python 2.7 standard library includes a module named `json`. Use it.
`django.utils.simplejson` is deprecated.