This fixes #34, salt version 2015.5.x needs an extra argument
for shell routines.

This state manages /etc/ssh/ssh_known_hosts and fills it with
public SSH host keys of other minions.

This will add more options to set to secure openssh
- AllowUsers
- AllowGroups
- DenyUsers
- DenyGroups

This fixes an issue where PyYAML was converting yes and no into True and False in the generated sshd_config file.