マルチスレッドとfilter 機能を追加

Squashed commit of the following:

commit 95bc7511f4390aa1c53eb221d8b05fbda4dc28b1
Author: Yuu ISHIKAWA <yuu.ishikawa@gmail.com>
Date:   Fri Jun 28 10:18:52 2013 +0900

    add_partition.rb に --filter を追加

commit 13fbb4b1b12deafdbb2019fed784419d95463a38
Author: Yuu ISHIKAWA <yuu.ishikawa@gmail.com>
Date:   Thu Jun 27 17:04:26 2013 +0900

    add_partition のマルチスレッド対応