events page refactor

[derekeder]

From #314 (review) by @fgregg there are a number of improvements we can make to the events listing page now that we have all the view code brought in:

        context = super(EventsView, self).get_context_data(**kwargs)

        # Get year range for datepicker.
        aggregates = ChicagoEvent.objects.aggregate(

this could be improved a good bit by not using the parameter, but instead defining two url rules

the current:

url(r"^events/$", views.EventsView.as_view(), name="events")

which would dispatch to the default upcoming events and

url(r"^events/(?P<date>\d{4}-{2}-{2})/$", views.MonthEventsView.as_view(), name="events"),

which dispatched to new view for just that selected month.

            org_select_events = []

            for event_date, events in itertools.groupby(select_events, key=day_grouper):

it would be very nice to push this grouping logic into the templates with the regroup tag.

https://openfolder.sh/grouping-in-django-templates