fix SuspiciousOperation in regex filters

The SuspiciousOperation is raised here if the read of the image gets
permissioned denied. In many cases where this is wrong it is because the
path given is /media/... which may refer to MEDIA_ROOT not /media.
make regex filters replace MEDIA_URL prefix in paths

MEDIA_URL prefixes are replaced with MEDIA_ROOT
Merge branch 'master' of github.com:mariocesar/sorl-thumbnail into filters
Merge branch 'master' of github.com:mariocesar/sorl-thumbnail into filters
fix hash in tests filter tests
Merge pull request #290 from etanol/master

New DBM based Key-Value Store
More backward compatible image_info option processing

Some older (but useful) sorl engines may not pass 'image_info' to write method. This lead to KeyError when using with sorl >= 11.12.1b
Merge pull request #303 from GeyseR/patch-1

More backward compatible image_info option processing
add test config for django 1.7
fix #309 when THUMBNAIL_PRESERVE_FORMAT=True and remote images
Merge pull request #310 from mgaitan/fix309

fix #309, fix _get_format for images with urls
Update compat.py
Update current.py
add django.setup() in test runner for django1.7
Update compat.py

optimizing condition of image format
Update current.py

Optimizing condition of image format
Fix broken cropping with upscale=False
remove unnecessary function call
Merge pull request #314 from renecarvalho/suport-png-mixin

Suport png mixin in django admin
Update test settings and utils for Django1.7

 - Set package name explicitly on INSTALLED_APPS. Fixes "Item" import
   issue.
 - Add MIDDLEWARE_CLASSES to suppress warning.
 - Add "enter" keyword to util sending ``setting_changed`` signal:
   https://docs.djangoproject.com/en/dev/releases/1.7/#signals
 - Change ``mimetype`` to ``content_type``
   https://docs.djangoproject.com/en/dev/releases/1.7/#features-removed-in-1-7