Merge branch 'redesign-timeline-generator' into 'master'

main.py

notify/calendar/__tests__/test_calendar.py

notify/calendar/__tests__/test_usual_calendar.py

notify/calendar/calendar.py

notify/calendar/rules/__tests__/test_exclude_dow.py

notify/calendar/rules/exclude_dow.py

notify/calendar/rules/loader.py

notify/channels/vonage_sms.py

notify/messages/__tests__/test_generator.py

notify/messages/generator.py

notify/messages/notification.py

notify/timeline/__tests__/test_basic.py

notify/timeline/basic.py

notify/timeline/iterator.py

requirements.txt

templates/daily-short.j2

templates/daily.j2