add filter to agent/label hierarchy in comment
Merge pull request #509 from kiyoto/agent-label-diagram

add filter to agent/label hierarchy in comment
fix router is nil inside out_copy, out_roundrobin, and BufferedOutput secondary.
In addition, set default router to be root_agent.event_router to avoid nil error in 3rd party plugins
Merge pull request #508 from fluent/router_out_copy

fix router is nil inside out_copy, out_roundrobin, and BufferedOutput secondary
Use private instead of protected
v0.12.1
in_monitor_agent renders Filter plugins
Merge pull request #514 from fluent/filter-support-in-monitor-agent

in_monitor_agent renders Filter plugins
filter out if #filter method returns nil record
rewrite filter_grep using new filter plugin API
Merge pull request #515 from fluent/filter_nil

filter out if #filter method returns nil record
Support @label by TestDriver
Merge pull request #517 from fluent/test_driver_routing

Support @label by TestDriver
Improve FilterTestDriver API

- Add run, emit and getting result methods
- Use new API in existing tests
Merge pull request #519 from fluent/improve-filter-test

Improve FilterTestDriver API
v0.12.2