Memory can't be pickled/unpickled.

It defines __reduce__ to exclude a timestamp from the pickle.

But __reduce__ includes:

        return (self.__class__, (location, self.backend, self.mmap_mode,
                                 compress, self._verbose))

where __init__ is:

    def __init__(self, location=None, backend='local', cachedir=None,
                 mmap_mode=None, compress=False, verbose=1, bytes_limit=None,
                 backend_options={})

cachedir, not mmap_mode is now the third positional argument. Perhaps it should be the last, and then __reduce__ need not be changed. Or __reduce__ can be fixed and changed again when the deprecation is completed.