re-apply changes from #91 for a clean commit history
remove `#quiet_system` as it is dead code by now
Call #validate_ssh_options! in ssh tests
Add --ssh-user option
Merge pull request #156 from tknerr/windows-compat

Windows Client Compatibility - Take 2 with Clean Commit History
Merge pull request #179 from tmatilai/ssh-user

Support `--ssh-user` option