replace cdn.mathjax.org with cdnjs

cdn.mathjax.org is shutting down: https://www.mathjax.org/cdn-shutting-down/

This changes the default MathJax URL in the math plugin, as well as
references in README.md and test/examples/math.html

1 files changed, 1 insertions, 1 deletions

diff --git a/README.md b/README.md
index 8e31935..2991ed1 100644
--- a/README.md
+++ b/README.md
@@ -1137,7 +1137,7 @@ Reveal.initialize({
 	// other options ...
 
 	math: {
-		mathjax: 'https://cdn.mathjax.org/mathjax/latest/MathJax.js',
+		mathjax: 'https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.0/MathJax.js',
 		config: 'TeX-AMS_HTML-full'  // See http://docs.mathjax.org/en/latest/config-files.html
 	},