Automated build of editors' drafts in COGA repository now working

It's been a concern for a while that the documents maintained in the 
COGA GitHub repository aren't up to date at the official editors' draft 
URI, which begins with w3c.github.io/coga. Instead, people have needed 
to use rawgit a lot.

I finally have a build system working that updates the w3c.github.io 
content whenever changes are pushed to the master branch. It will *not* 
update when changes are pushed to other branches (e.g., working 
branches), you can still use rawgit for those. But the content of the 
master branch, which should reflect consensus content, will now be kept 
up to date.

There are most likely tweaks needed to this. But the basic process now 
works.

Michael