Research: ruby ssh client and server

[mikehale]

Try establishing an ssh session by using a pure ruby client and server.

Ref: https://github.com/net-ssh/net-ssh/blob/df1729ed70cebe7a952effb9c5fd5f8ff3e50000/lib/net/ssh/transport/session.rb#L70, https://github.com/hirura/hrr_rb_ssh#starting-server-application