update Gemfile, add timecop gem
bundle install
update spec_helper.rb, add require-path for helper method
create event_helper_spec.rb

setup test for "within_one_year?" method
update event_helper_spec.rb
update event_helper_spec.rb

add some cases for "within_one_year?" method
Merge branch 'event_helper' of github.com:gouf/shirasagi into gouf-event_helper
Merge branch 'gouf-event_helper'