Memoize computing excerpt's relative_path (#6951)
Memoize computing excerpt's relative_path (#6951)

Merge pull request 6951
chrisfinazzo/jekyll,tillgrallert/jekyll,jekyll/jekyll,tillgrallert/jekyll,x-way/jekyll,yhironaka/yhironaka.github.io,jekyll/jekyll,tillgrallert/jekyll,x-way/jekyll,x-way/jekyll,jaybe-jekyll/jekyll,ryanshaw/jekyll,Strangehill/jekyll,fulldecent/jekyll,jekyll/jekyll,chrisfinazzo/jekyll,chrisfinazzo/jekyll,getandpost/jekyll.github.io,tillgrallert/jekyll,jaybe-jekyll/jekyll,fulldecent/jekyll,Strangehill/jekyll,x-way/jekyll,tillgrallert/jekyll,fulldecent/jekyll,jaybe-jekyll/jekyll,ryanshaw/jekyll,Strangehill/jekyll,jekyll/jekyll,ryanshaw/jekyll,fulldecent/jekyll,jaybe-jekyll/jekyll,chrisfinazzo/jekyll,Strangehill/jekyll,ryanshaw/jekyll,getandpost/jekyll.github.io,getandpost/jekyll.github.io,Strangehill/jekyll