Updated the PKGBUILD to 0.9.12

- Changed deprecated build() to package()
- Using pkgver in the source binary urls
- Added a >=1.6.2 version dependency for python2-django

The django dependency results from changes in manage.py that got deprecated
and are no longer present in django 1.6. Due to this change this package would
not work on Archlinux since the upstream adopted the change but the package
remained with the deprecated code.