Fix south integration with `--create-db`

This requires to monkey-patch `south.hacks.django_1_0.SkipFlushCommand`,
which prevents the initial data to be installed.

South issue: http://south.aeracode.org/ticket/1395#comment:3

Fixes https://github.com/pelme/pytest_django/pull/22

Django code reference for 1.6, from
django-1.6.x/django/db/backends/creation.py(339)create_test_db():

    # Report syncdb messages at one level lower than that requested.
    # This ensures we don't get flooded with messages during testing
    # (unless you really ask to be flooded)
    call_command('syncdb',
        verbosity=max(verbosity - 1, 0),
        interactive=False,
        database=self.connection.alias,
        load_initial_data=False)

    # We need to then do a flush to ensure that any data installed by
    # custom SQL has been removed. The only test data should come from
    # test fixtures, or autogenerated from post_syncdb triggers.
    # This has the side effect of loading initial data (which was
    # intentionally skipped in the syncdb).
    call_command('flush',
        verbosity=max(verbosity - 1, 0),
        interactive=False,
        database=self.connection.alias)