Chapter email info

[geobrando]

Currently we're storing organizer twitter but not chapter email address in chapters.json. Email is not dead. We could add this field to the properties object and render at maptime.io/chapters.

A better alternative could be to add it to the _config.yml of the starter template and make some changes so that it is rendered on chapter sites. For those rolling with their own custom websites, it'll be up to them to decide if and how to display.