Correct not to display link to current page on root path

app/helpers/application_helper.rb
- Correct main_links() not to display link to current page
  when it's on root path.
Update holly_test.rb for holiday test data up to 2014-3-21

test/unit/lib/holly_test.rb
- Update HOLIDAYS up to 2014-3-21.
- Alter test_holiday_q() to get the values for date_from and
  date_to from HOLIDAYS, eliminating DATE_FROM and DATE_TO.
'approval_statuses#index' to display AdHocWork#description (show/hideable)

app/assets/javascripts/approval_statuses.js
- Newly created.
app/assets/javascripts/approval_statuses.js.coffee
- Removed from the repository.
app/assets/stylesheets/style.css
- Add '.toggle_show_hide' and '.show_hide_able'.
app/views/approval_statuses/_status_table.html.erb
- Add HTML attribute label_show, label_hide, tooltip_show and
  tooltip_hide to the <table> to be used in approval_statuses.js.
- Display <td> to be to work as a button to show/hide detail and
  AdHocWork#description (initially-hidden) if the model is AdHocWork.