Allow options for custom ssh port

Closes #12

Where custom portnumber is 5858 - This pull request allows 

tugboat ssh fuzz -p 5858
tugboat ssh fuzz --ssh-port=5858

`  -p, [--ssh-port=SSH_PORT]  # The custom SSH Port to connect to`

It also allows a global port number configured in ~/.tugboat

Woohoo! My life is now complete :-)