### Proxy bouncing support
- Add multi-level proxy bouncing support with new syntax
  eg. proxytunnel -p local-proxy:port -r remote-proxy1:port -r remote-proxy2:port -d %h:%p

- Add proxy bouncing authentication support with new syntax
  eg. proxytunnel -p user@local-proxy:port -r user@remote-proxy:port -d %h:%p
  or: proxytunnel -p username:password@local-proxy:port -r username:password@remote-proxy:port -d %h:%p


### Code cleanup
- Find some hardcore C experts to help us improve the code quality

- Improve the error output, make it consistent throughout the program

- Add different verbosity-levels (with or without data exchange)

- Get rid of the "ssh_exchange_identification: Connection closed by remote host"
  message when proxytunnel fails to set up tunnel. proxytunnel should give a
  sensible cause instead of the weird ssh error.
  (Users need to understand that proxytunnel fails, not ssh itself)


### Add default test-cases
- Before releasing proxytunnel, we should validate the different error-cases
  + local proxy does not exist (unresolvable)
  + local proxy exists but does not answer (tcp timeout)
  + local proxy does not talk HTTP
  + local proxy is not a proxy (does not accept CONNECT)
  o remote proxy does not exist (unresolvable)
  o remote proxy exists but does not answer (tcp-timeout)
  + remote proxy does not talk HTTP
  + remote proxy is not a proxy (does not accept CONNECT)