can't build whl package due to setup.py referencing packaged to be installed

setup.py shouldn't refer to the module that setup.py is meant to be installing, since the user may not have the dependencies installed yet!

This breaks pip wheel functionality:

```
pip wheel django-notifications-hq
Downloading/unpacking django-notifications-hq
  Downloading django-notifications-hq-0.6.0.tar.gz
  Running setup.py egg_info for package django-notifications-hq
    Traceback (most recent call last):
      File "<string>", line 16, in <module>
      File "/tmp/pip_build_joel/django-notifications-hq/setup.py", line 2, in <module>
        from notifications import __version__
      File "notifications/__init__.py", line 7, in <module>
        from notifications.urls import urlpatterns
      File "notifications/urls.py", line 5, in <module>
        urlpatterns = patterns('notifications.views',
    NameError: name 'patterns' is not defined
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):

  File "<string>", line 16, in <module>

  File "/tmp/pip_build_joel/django-notifications-hq/setup.py", line 2, in <module>

    from notifications import __version__

  File "notifications/__init__.py", line 7, in <module>

    from notifications.urls import urlpatterns

  File "notifications/urls.py", line 5, in <module>

    urlpatterns = patterns('notifications.views',

NameError: name 'patterns' is not defined
```

Sorry for the extra commits in the PR. I was attempting to keep using the version defined in `notifications/__init__.py` before realising this is a bad thing and very few if any other setup.py files refer to the modules they install.