Autobuild: Clone over https (no auth reqd)
Autobuild: Vendor pandoc bin and use it
Autobuild: make `build` easily callable externally
Autobuild: create basic autobuild script
Output one PDF per lesson.

This was just for testing anyway.
Also, remove `pdf_generator` = 'all' option.
Autobuild: attempt to get file zipping working
Merge pull request #91 from andylolz/autobuild

Autobuild lessons