Fix the requirements for a django library

Change from django_pyscss to django-pyscss
This is required because that is the way this library
is registered on PyPI. This is the link:
http://pypi.openstack.org/simple/django-pyscss/

Change-Id: I02cb1022f93dc03ba669db3899090cd2cc552066
Closes-bug: #1339918
Merge "Fix the requirements for a django library"