Feature request: unix socket forwarding

## Affected Version
v1.0.1

## Expected Behavior
It should be able to forward unix sockets like ssh does.
For example, configuration would look like this:
```
--source unix://$HOME/.docker/docker.sock \
--destination unix:///var/run/docker.sock \
```

## Current Behavior
```
ERRO[0000] missing port in destination address: unix
```

