TO-DO
=====

* allow setting chmod bits on SFTPClient.open() for create
* host-based auth (yuck!)
* ctr forms of ciphers are missing (blowfish-ctr, aes128-ctr, aes256-ctr)
* sftp protocol 6 support (ugh....) -- once it settles down more
* make a simple example demonstrating use of SocketServer (besides forward.py?)
* should SSHClient try to use openssh config files?
* figure out how to parse ssh.com encrypted key files?
* is it possible to poll on a set of events at once?
* potentially create only one thread shared by all Transports
* SSHClient: flag to turn off agent detection? flag to turn off keyfile discovery?