Add unified logging of Docker containers

[saidimu]

fluentd or logstash? Seems fluentd for now:

• http://jasonwilder.com/blog/2013/11/19/fluentd-vs-logstash/
• http://www.fluentd.org/guides/recipes/syslog-influxdb
• http://blog.librato.com/posts/collector-patterns

[saidimu]

An alternative approach?

• https://blog.logentries.com/2015/02/what-is-the-docker-stats-api/