Updating pool_manager to fix NameError problem

pool_manager kept producing NameErrors in calls.rb:33 because it was not forwarding the "method" method call and "respond_to?" method properly to the @worker_class.
Removing code duplication in pool_manager.rb
Merge pull request #472 from stephan-nordnes-eriksen/patch-1

Updating pool_manager to fix NameError problem