New Feature: Multiple remotes, same connection

[davrodpin]

App should allow to specify multiple -remote, so user could access multiple services through the same tunnel, reusing the same connection.

Example:

$ mole -remote host1:3306 -remote host2:80 -remote host2:443 -server my-ssh-server
INFO[0000] listening on local address                    remote="host1:3306", local_address="127.0.0.1:64723"
INFO[0000] listening on local address                    remote="host2:80", local_address="127.0.0.1:64724"
INFO[0000] listening on local address                    remote="host2:443", local_address="127.0.0.1:64725"

If multiple -remote are specified, then -local can't be used.

let me know if anyone has another suggestion for how to specified the local port for each host without combining -remote and -local in one single flag).

[davrodpin]

#72