Added respond with empty image for Issue #86 based on work by @parolkar
Add Fluent::Parser class for Parser plugins
Add Fluent::Formatter class for Formatter plugins
Add Parser#parse method for clear and consistent API

'call' is not clear method name for 'parsing text' behaviour.
'call' still exist for existing plugins but 'parse' is recommended from now.
Merge pull request #499 from fluent/add-filter-and-parser-classes

Add Parser and Formatter base classes
Merge remote-tracking branch 'github/master'
Made the 1 pixel image a constant
Added tests for respond_with_empty_img
Remove unused require_id method from PluginId
Prevent an exception with large num_retries.

If the calculated wait time is infinite, don't try to do
further calculations on it to prevent it from becoming NaN.
This could happen if num_retries becomes too large (>1024).
Fixed option type from string 'false' to false
Updated test after hitting an issue with [Net:HTTP encoding](https://bugs.ruby-lang.org/issues/2567), thanks to @kioto for the help with this
Fixed in_httpd test for Ruby 1.9.3 by forcing the encoding on EMPTY_GIF_IMAGE
Merge pull request #480 from Telmo/master

Add respond with empty image
Refactor in_monitor_agent to remove unnecessary instance eval
reorder conditional to handle NaN or Infinite
Merge pull request #502 from mr-salty/fix-max-retry-exception

Prevent an exception with large num_retries.
Accept '@type' and '@id' in v1 configuration. fixes #500

Plugin type and id are system reserved parameters like @label.
So using '@' prefix is better for separating normal plugin parameters.
in_monitor_agent supports '@type' and '@id' query
Merge pull request #503 from fluent/at-prefix-for-type-and-id-parameters

Accept '@type' and '@id' in v1 configuration. fixes #500
Fix tag parameter handling in in_monitor_agent
Fix blank handling of TSVParser. fixes #505