Update django_orphaned/management/commands/deleteorphaned.py

Needed files were crafted using the name of their directory (a folder in MEDIA_ROOT) and their file name in database, which is relative to MEDIA_ROOT.
So if you want to check folder/media/images for orphaned files, it will create a list of needed files in the following form : folder/media/images/images/file.ext, which is always wrong unless you upload files directly in MEDIA_ROOT.
Merge pull request #3 from artscoop/patch-1

Update django_orphaned/management/commands/deleteorphaned.py