Make salmon comptaible with salt-ssh

[rbu]

Since 0.17, salt provides the "salt-ssh" command that allows running against minions that do not have salt installed, but are configured via a roster file.
It would be nice if salmon was flexible enough to call salt or salt-ssh, depending on configuration.
It already has a configurable SALT_COMMAND, but it appends "--static", an option not allowed by salt-ssh.

[ipmb]

Please check out the new version (0.2.0) which no longer requires SALT_COMMAND and should work with salt-ssh.