Get days

うーん...
Merge pull request #23 from tatsuo/spike_calendar

Date.nowが２回なのがちょっと気になるけど、次に進んでみようー。
Move days to helper
Add i18n
Add spec ApplicationHelper#days_of_a_month
Refactor duplicatited DateTime.now
Merge pull request #24 from tatsuo/spike_calendar

Spike calendar ( refactor )