Quicker categories for documents without superdirs (#7987)
Quicker categories for documents without superdirs (#7987)

Merge pull request 7987
chrisfinazzo/jekyll,x-way/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,jekyll/jekyll,chrisfinazzo/jekyll,jekyll/jekyll,x-way/jekyll,ryanshaw/jekyll,jaybe-jekyll/jekyll,jaybe-jekyll/jekyll,yhironaka/yhironaka.github.io,chrisfinazzo/jekyll,ryanshaw/jekyll,ryanshaw/jekyll,fulldecent/jekyll,fulldecent/jekyll,jekyll/jekyll,jaybe-jekyll/jekyll,x-way/jekyll,chrisfinazzo/jekyll,fulldecent/jekyll,fulldecent/jekyll,jekyll/jekyll