Merge pull request #225 from Scotchester/gh-pages

Pre-clearance edits
Merge pull request #226 from Scotchester/gh-pages

Improve footer responsiveness, update README sitemap
Adjust headings for accessibility guide for better structure.
Make link text more descriptive on Accessible interfaces page.
Add text alternative to external link icon.
Update text alternative for external link icon. Now is broader.
Adjust visual hierarchy only.
Merge pull request #228 from Scotchester/gh-pages

Edits from clearance feedback
added "visual" before the word "identity"

per @mebates request in issue #238.
Merge pull request #234 from davidakennedy/gh-pages

Adjust headings for accessibility guide for better structure.
Remove unnecessary character in URL to Flickr
Merge pull request #249 from ohsk/gh-pages

Remove unnecessary character in URL to Flickr
Fix instances of Avenir Next not rendering

Also removes outdated/no longer used stuff.