Change the log output directory.

- from: /var/lib/webaap/apps/gcal2dailyplanner/log
- to  : /var/log/gcalendar

This commit refs #4.
Specify `@dir` variable, under production environment.

This commit refs #4.
Merge pull request #4 from kazu634/id/4

ログ出力ディレクトリを`/var/log/gcalendar`とする