fix system config uses double memory
Add Plugin.new_formatter to create Formatter plugin
Add Plugin.new_parser to create Parser plugin
Merge pull request #497 from fluent/add-new-xxx-api-to-parser-and-formatter

Add new_xxx api to parser and formatter
Merge pull request #496 from fluent/fix_system_config

Fix system config using double memory
Remove unused argument from add_label
Add basic Input test
Add FilterTestDriver and update Filter tests
Fluent::Test moved to fluent/test/base.rb
out_test plugin moved to under test directory
Merge pull request #498 from fluent/test-module-moved-to-test-base

Test related code moved to under test directories