Support using chef-zero in SSL mode.

This defaults to true because it's what we should be using, but
config files should turn it off if they're not ready.
Merge pull request #12 from jaymzh/ssl

Support using chef-zero in SSL mode.
Better error handling

* Exit if we fail to setup a host
* If we are going to exit for something it's an error, not a warning
Merge pull request #14 from jaymzh/error

Better error handling
Support telling chef-zero to log.

Won't commit until after opscode/chef-zero#103 is in.