HTML Proofer: Add to Travis build
Documentation: Fix bad download anchor link
Build: Compile Event page SCSS

This was showing up as missing since it wasn’t compiled or copied to
diet
Build: Skip creating test pages on dist

The page requires other JS files to be copied that aren’t included as
part of the dist build
HTML Proofer: Relax failures

 - The additional "#" anchor that is correctly escaped in the Geomap
demos can be ignored.
 - The query fragment in French text highlight demo appears to have
characters that may need to be escaped. This is also the reason the
encoding direct is now required in the Rakefile.
Tablevalidator: Fix casing on category frontmatter
Test: Correct frontmatter for language toggle

Pointing to the index since there is no generated French test harness.
Merge pull request #6048 from nschonni/travis-html-proofer

Build: Run html proofer on Travis