Add rudimentary progress on fusepy support

* Run ./paranoia_fuse.py [username] [mountpoint] to generate a private key
  at [username].pem, and connect to the running server at [mountpoint]/.
* Run ./paranoia_fuse.py [username] [mountpoint] [privatekey.pem] to reload
  that private key (otherwise, you'll register again).
* Commands ls, mkdir (getattr) work.