Adding needed mock requirement

When using kotti_settings on a fresh kotti install, I get this traceback :

    File "***/local/lib/python2.7/site-packages/kotti_settings-0.1-py2.7.egg/kotti_settings/tests/test_events.py", line 1, in <module>
         from mock import patch
    ImportError: No module named mock

My fix for this was to add mock in the setup.py requirements.