Prevent empty chapter pages

[geobrando]

Any repo in the maptime org with a gh-pages branch is by default served at maptime.io. Currently, this includes copies of the cloned starter page which have yet to be customized and used in any way. Some of these are linked to directly from the chapters page. This is because new chapters are automatically given the starter repo whether or not they want one or are ready to use it.

The starter template is pretty much useless you've added posts or events. It would be useful if there were a way to prevent these from being served until they've been configured and are ready to use. At a bare minimum, we should probably clone these only at the request of fully-formed chapters.