Added second parameter to SupervisionGroup.pool method to pass options hash

[bsingr]

Now you can do something like the following:

class MyGroup < Celluloid::SupervisionGroup
  pool Worker, as: :worker_pool
end

Without this patch the same can be done using the following:

class MyGroup < Celluloid::SupervisionGroup
  supervise Worker, as: :worker_pool, method: 'pool_link'
end

[tarcieri]

Thanks!

[travisbot]

This pull request fails (merged 5b711e8 into b58b34e).