Remove `max_length=255` from `Event.recurrence_rule` field.
Remove `max_length=255` from `Event.recurrence_rule` field.

ic-labs/django-icekit,ic-labs/icekit-events,ic-labs/django-icekit,ic-labs/django-icekit,ic-labs/django-icekit,ic-labs/icekit-events,ic-labs/icekit-events