Remove debug code
Haineko does fork() when the number of recipients is greater than 1
Define the default value of "max_workers"
use Parallel::Prefork instead of Paralle::ForkManager
New configuration field: max_workers for fork()
Use Paralell::Prefork 0.14 or later instead of Parallel::ForkManager
Release notes of Haineko 0.2.10 as a draft