Add support for sftp

[codebynumbers]

Add an abstraction layer so this can also be used to wrap pysftp

[meetchandan]

hey - is this done?

[codebynumbers]

No it is not.

[byteskeptical]

I worked on this after pysftp didn't quite fit my needs and it seemed to be unmaintained. More than happy to collaborate on such an en devour.

https://github.com/byteskeptical/sftpretty