update highlight.js url

README.md

@@ -589,7 +589,7 @@ Reveal.addEventListener( 'fragmenthidden', function( event ) {
 
 ### Code syntax highlighting
 
-By default, Reveal is configured with [highlight.js](http://softwaremaniacs.org/soft/highlight/en/) for code syntax highlighting. Below is an example with clojure code that will be syntax highlighted. When the `data-trim` attribute is present surrounding whitespace is automatically removed.
+By default, Reveal is configured with [highlight.js](https://highlightjs.org/) for code syntax highlighting. Below is an example with clojure code that will be syntax highlighted. When the `data-trim` attribute is present surrounding whitespace is automatically removed.
 
 ```html
 <section>