* matthewwithanm/whencontrol:
Rename cache_state_backend to image_cache_backend
Add NonValidatingCacheStateBackend
Some documentation
Only invalidate spec file if source changes
Rename DefaultCacheStateBackend
generate method (optionally) saves file
Rename force flag to force-revalidation
Add clear method for when future validation is unwanted
Commands for validating and invalidating the cache
Fix var name typo
Spec files now accessible through _ik attr
Remove unused import
First shot at cache state backend implementation
Conflicts:
imagekit/models/fields.py