Fixed silent fail with use of ~ homedir shortcut

[poltak]

• adds in new package expand-home-dir (this may not be welcome)
• simply traverses the servers.pem string and expands ~ into the full homedir path, if present, via function exposed by package
• previously path.resolve() could not handle the ~ shortcut and would cause the SSH connection to (silently) fail in the deploy and setup commands
• works with both servers.pem strings containing ~ and absolute paths
• fixes Using "~" in pem is making mup silently fail #189

[madushan1000]

Hi @poltak,
Thank you for the pr.
Could you refactor this into more general solution so that any path used in the config file has homedir expansion?

[avishaan]

@madushan1000 although I agree this is a problem with other directories, it makes sense that you go and merge this one at least. This is literally the problem raised in #291, #286, #135, #87, #245, #42, #222, #179 with the oldest one being 9 months old