Install cnx-query-grammar and plxslt in .travis.yml
Move most of to_html.py into cnx-archive to avoid circular dependency
Move collection minor version migration from cnx-archive to cnx-upgrade
Move buylink migration from cnx-archive to cnx-upgrade
Merge pull request #8 from karenc/remove-cnx-upgrade-dependency

Moves cnx-archive dependent elements to remove the circular dependency. Also places the buylink script in this package.