Add service discovery section and Consul.

Consul is a tool for service discovery, monitoring and configuration.
Add ZooKeeper to service discover section.

ZooKeeper is a centralized service for maintaining configuration information,
naming, providing distributed synchronization, and providing group services.
Add Doozerd to service discovery section.
Merge pull request #68 from bdossantos/service_discovery

Add service discovery section with Consul, ZooKeeper, Doozerd ...