Add 'alias' option to config_section and config_param
 * To allow plugin authors to define alias name of configuration attributes
   * An valid attribute name in standard configuration syntax, MAY conflicts ruby reserved keywords in DSL
   * An valid attribute name in DSL, MAY conflicts in Fluentd configuration syntax keywords
add tests for bool value setting without default values
Merge pull request #402 from tagomoris/alias_config_attributes

Add 'alias' option to config_section and config_param
[WIP] ACK prototype works
Extract recv_with_timeout

divide error checks into check of timeout and check of ack
Add receive_response_timeout option
Change argument type

proc  ->
block
Fix: access log by @log

$log ->
@log
Send response also when receiving Forward or Message
Add tests for ForwardInput to respond or not to respond

But in some cases, socket is closed before response has been read.
So something needs to be fixed.
Fix: sending data need to include option