Raise South requirement

Require South 1.0 so that we can prepare for using Django 1.7 native
migrations in future (at point where we drop Django 1.6 support).

Signed-off-by: Michal Čihař <michal@cihar.com>
Rename South migrations directory

Rename directory holding South migration so south_migrations. This is
needed for future migration to Django 1.7 migrations.

See South migration guide for more details:
http://south.readthedocs.org/en/latest/releasenotes/1.0.html#library-migration-path

Signed-off-by: Michal Čihař <michal@cihar.com>
Update requirements in spec file

Signed-off-by: Michal Čihař <michal@cihar.com>