Merge pull request #157 from martinb3/master

Remove logic that is already in elkstack::agent
Merge pull request #158 from martinb3/master

Don't converge elkstack* until we find servers
Add a hash to use to configure custom logstash

RE: https://github.com/rackspace-cookbooks/platformstack/issues/160

This is better than each wrapper trying to detect if elkstack / logstash are converged and trying to send notifications to resources that may or may not exist.