Merge pull request #1 from ha1t/support_normal_chatwork

www.chatwork.comでも使えるように
Merge pull request #2 from ha1t/develop

iconとりあえず追加
( http://www.iconarchive.com/show/colorful-long-shadow-icons-by-graphicloads/Stamp-icon.html )
stamp sheet menu
import/export
check json format
Merge pull request #3 from makiuchi-d/import-export

シートのimport/export