Modify: remove feature "ignore_list"
This commit removes a feature "ignore_list". Use new feature "nodup" instead of "ignore_list". With this change, any value returned by a Proc registered by hook that is not true, false, nil, etc. will now be converted to a string and output. ---- $ seq 1 3 | ./outvoke.rb -q -e 'hook("stdin") { _1.body.to_i * 2 }' 2 4 6 ----