List all events

[martinheidegger]

This is a request in response to https://github.com/nodeschool/newsletter/issues/12.

After the chapter specification is decided it would be good to have not just a list of chapters but also of a list of events. Preferably with a start and end selector that allows to get only the events within a certain period and only show the events for a chapter if a chapter is selected.

Note: this is necessary because we have events outside of chapters at the google docs form!