Fix ReST error that breaks rendering on PyPI

Running 'python setup.py register' should be sufficient to upload the new long_description to PyPI and make https://pypi.python.org/pypi/django-nose pretty enough.  

Alternatively you can edit the description field and add the missing '~' character by hand there.
Merge pull request #139 from mgedmin/patch-1

Fix ReST error that breaks rendering on PyPI