added user#digest_frequency to represent the user preference for notification mechanism
added schedule_notification model to queue notifications as they occur
added whenever for crontab manipulation using rake tasks
added visual specs in account#edit for digest frequency selection
added visual digest email representation following immediate emails spec
added simplecov for coverage representation
added snippet in task db:recreate for users' crontab manipulation (env aware)
added cron:daily and cron:weekly as main controller calls for periodic notification digest
added services/notifications.rb for dealing with cron job business logic under Notifications::Digest.daily and Notifications::Digest.weekly according the user's digest frequency option
user#digest_frequencyto represent the user preference for notification mechanismschedule_notificationmodel to queue notifications as they occurwheneverfor crontab manipulation using rake tasksaccount#editfor digest frequency selectionsimplecovfor coverage representationdb:recreatefor users' crontab manipulation (env aware)cron:dailyandcron:weeklyas main controller calls for periodic notification digestservices/notifications.rbfor dealing with cron job business logic underNotifications::Digest.dailyandNotifications::Digest.weeklyaccording the user's digest frequency option