Read sudo_prefix from config file

[paneq]

This is first step to allow to overwrite some Fabric default values via config file. I personally needed to set sudo_prefix in config file:

[ssh]
sudo_prefix =sudo -E -S -p '%(sudo_prompt)s'

The additional -E switch for sudo preserves environment variable which in my case was SSH_AUTH_SOCK that I needed so that chef user can log into another machines using ForwardAgent ssh option when running one of the recipe.

[tobami]

Would't this be fixed once #59 is implemented?

[paneq]

I guess not. You still need to preserve environment to have agent forwarding working under sudo command.