"kamaki file cat" can now output data as they are being downloaded
It is also safe to pipe it
The new library method "stream_down" is implemented in
    "kamaki.clients.PithosClient" and it sequentially downloads
    parts of a remote object to a buffer, which is then written to
    the destination. The destination descriptor is prepared and
    provided by the caller (i.e., "kamaki file cat"). Each part of
    the object is downloaded asynchronously, though.