Add support for port and different identity file in ssh config

[gnufied]

it would be nice if slaves section can take ssh port and identity file as well. It will be much easier to test buffet with something like vagrant then.

[sds]

Hey @gnufied,

This is a great idea. Writing some integration tests to work with Vagrant would be interesting to try out.

Rather than just allowing the identity file to be changed, it would probably make sense for Buffet to allow you to specify the ssh config file itself, and pass that in via ssh -F <file>.

Our infrastructure at @causes uses Chef to provision the cluster we use for running the Buffet slave, including the ssh config for the user running the Buffet master, so this isn't something I can say we'll be adding ourselves soon (but would certainly merge a pull request).

Your comments and suggestions are always welcome. Thanks for using Buffet!