Added support for identity files.

[dbtlr]

Currently, if you're using a custom ssh key for a particular server, you cannot use this plugin to SCP for you. This adds options support for a identity_file key, which allows you to specify the full path to a id_rsa ssh private key, to pass through in the -i option for scp.

[hydralien]

Hey Drew,

I know it's kinda too late to reply to this, but as I'm picking up the maintenance of this project (in my fork of it), wanted to still leave a comment here.
I think the functionality you're aiming to achieve here is covered by IdentityFile parameter in ~/.ssh/config (or wherever your OpenSSH config is - not sure where it is on Windows), e.g. http://www.cyberciti.biz/faq/force-ssh-client-to-use-given-private-key-identity-file/

Cheers,
Boris