Merged changes from branch gh-pages.
Added link to demo and mla13 archive and fixed a few other links.
Speed: Add column labels for known TAGS versions so they do not need to be pre-fetched.
Updated JavaScript library versions.
Speed: Template strings are WAY faster than DOM-based <script> templates. Why?
Make educated guess if gid is missing.
You can now put a spreadsheet key in the query string; better spreadsheet URL validation.
Update bootstrap CDN version (merge from master).