Fix for projects using Django 1.4 layout

This pull request fixes [an issue](https://github.com/mbi/django-rosetta/issues/63) where locale directories one dir down from core app directory are ignored even though they are in the actual project root for Django 1.4 project layouts.

https://docs.djangoproject.com/en/dev/releases/1.4/#updated-default-project-layout-and-manage-py

Should work but feel free to suggest cleanups.