Secure shell proxy command

The command currently used for ssh proxy depends on netcat being installed on the bounce host.  As of OpenSSH v5.4, there is no need to do it this way as there is native support.  Migrate!

The current/old method:

``` bash
ProxyCommand="ssh ${bounce} nc %h.${tld} 22"
```

The new method can simply use:

``` bash
ProxyCommand="ssh ${bounce} -W %h:%p"
```
