Update CDN for MathJax (#6013)
Update CDN for MathJax (#6013)

Merge pull request 6013
ryanshaw/jekyll,Strangehill/jekyll,alex-kovac/jekyll,tillgrallert/jekyll,chrisfinazzo/jekyll,tillgrallert/jekyll,jekyll/jekyll,jaybe-jekyll/jekyll,Strangehill/jekyll,fulldecent/jekyll,chrisfinazzo/jekyll,fulldecent/jekyll,jekyll/jekyll,chrisfinazzo/jekyll,getandpost/jekyll.github.io,x-way/jekyll,tomjohnson1492/jekyll,tillgrallert/jekyll,fulldecent/jekyll,rasa2011/rasa2011.github.io,jaybe-jekyll/jekyll,rasa2011/rasa2011.github.io,jaybe-jekyll/jekyll,Strangehill/jekyll,gencer/jekyll,jaybe-jekyll/jekyll,tomjohnson1492/jekyll,rasa2011/rasa2011.github.io,gencer/jekyll,getandpost/jekyll.github.io,alex-kovac/jekyll,gencer/jekyll,tomjohnson1492/jekyll,alex-kovac/jekyll,Strangehill/jekyll,alex-kovac/jekyll,gencer/jekyll,chrisfinazzo/jekyll,ryanshaw/jekyll,Strangehill/jekyll,tomjohnson1492/jekyll,ryanshaw/jekyll,gencer/jekyll,ryanshaw/jekyll,x-way/jekyll,jekyll/jekyll,getandpost/jekyll.github.io,yhironaka/yhironaka.github.io,jekyll/jekyll,tillgrallert/jekyll,x-way/jekyll,tillgrallert/jekyll,x-way/jekyll,alex-kovac/jekyll,tomjohnson1492/jekyll,fulldecent/jekyll