- TODO: finish refactor work. Document new agent model of input+filter+output.
  All messages are arbitrary hashes now (encoding on wire is json)

  * Document it. 
  * Move 'Agent' to LogStash::Agent

  * Add inspectabilty to agents (Some kind of RPC to query status)
  
  Write examples:
  * log monitor agent (react/alert to messages over amqp, for example)
  * write storage agent (mongodb, elasticsearch, etc)
  * web frontend using websockets for real-time search through a browser