Requires ec2 with public DNS? #23

Hi

My machines do not have public addresses within my VPC and it seems to be a requirement of this package I think.

If this is the case can I suggest "def get_ssh_uri" in ec2 falls back to "private_dns_name"?

I also found my VPC settings were such that private DNS was not resolving so it maybe better if it altogether was able to fall back to IP address.

Maybe I'm missing something, I've not been using Fabric that long.

Cheers