add script directory for tmux and change a part of setup into abbreviation

tmux 用スクリプトディレクトリを追加と設定の一部を省略形に変更

Signed-off-by: pocozo3 <taka3@t3.rim.or.jp>
change the number of characters of the left status bar of tmux

tmux の左ステータスバーの文字数変更

Signed-off-by: pocozo3 <taka3@t3.rim.or.jp>