Cleaned up some author method documentation
Updated supported version of libgit2
Added dependency on pygments-cl-repl
Merged asdf system files into one

This uses the new / separator to designate child packages.
Cleaned up some API doc strings
Move change log off index page
Updated index page
Fixed up many documentation strings

This change also make the pages more consistent.
Added better index page and removed texinfo doc
Released 0.20.0