django.utils.simplejson is removed in django1.7

[ldrumm]

simplejson has been deprecated since the release of django 1.5; see https://docs.djangoproject.com/en/dev/internals/deprecation/#deprecation-removed-in-1-7 for details.

<...snip...>
  File "./local/lib/python2.7/site-packages/security/middleware.py", line 13, in <module>
    from django.utils import simplejson as json, timezone
ImportError: cannot import name simplejson