Support ssh_config Hostname

[wollerman]

First, thanks for creating this! You've saved us some time working through the ProxyCommand and ec2connect dance.

So far I've been able to successfully ssh ec2-user@<instance-id>. I typically like to add an entry to ssh_config so that I can ssh mynode. If I drop the instance-id into the Hostname field, however, it throws the following error:

ssh: Could not resolve hostname <instance-id>: nodename nor servname provided, or not known

I've also tried the public DNS. And If I use the IPv4 Public IP I get:

ec2-user@<public-ip>: Permission denied (publickey,gssapi-keyex,gssapi-with-mic).