The old PipelineCachedStorage class has been removed, because Django

removed the CachedStaticFilesStorage class. The reasoning here is that

this storage backend had non-specified "intractable problems". Django

advises to switch to ManifestStaticFilesStorage, and Pipeline does

have a storage class that inherits from this. This class does the same

hashing for filenames that the old cached storage does. The major

difference is that it also looks for those files in the manifest file.

This can be disabled via a class attribute, so I've added a subclass of

it that uses the backend for its hashing but turns off manifest

checking.

Ran unit tests.