Remove ADMIN_MEDIA_PREFIX reference in widgets.py
Remove ADMIN_MEDIA_PREFIX reference in widgets.py

To avoid a deprecation warning when using Django 1.4, removed the reference to ADMIN_MEDIA_PREFIX in widgets.py.
PetrDlouhy/django-smart-selects,johtso/django-smart-selects,uraniumanchor/django-smart-selects,olivierdalang/django-smart-selects,savoirfairelinux/django-smart-selects,moarcant/django-smart-selects,mkaluza/django-smart-selects,flibbertigibbet/django-smart-selects,savoirfairelinux/django-smart-selects,knixeur/django-smart-selects,digi604/django-smart-selects,digi604/django-smart-selects,knixeur/django-smart-selects,johtso/django-smart-selects,PetrDlouhy/django-smart-selects