disable for now
- offer more assistance if using a deprecated setting. If a plugin has:
    config :whatever, :deprecated => "some message'
  then the deprecated warning will include that message
- By popular request, deprecation of settings can now advise users about
a corrective action.

  config :whatever, :deprecated => "This is a nice message to help you
    fix something"
Merge git://github.com/logstash/logstash