monkey patch ssh transport for ssh config

Right now there is a bug in ansible wherein if you provide a 'Port'
configuration in an ssh configuration file, this will always be
overriden by '-oPort 22'. As our Vagrant setup uses ports other than
22 and because it is convenient to use an ssh_config file to specify
how to connect, we need to monkeypatch this transport provider.
Merge pull request #258 from craigtracey/monkeyssh

monkey patch ssh transport for ssh config