Update README.md

Changing the link to grunt.js installation instructions.

README.md

@@ -450,7 +450,7 @@ If you want to add a theme of your own see the instructions here: [/css/theme/RE
 
 ## Development Environment
 
-reveal.js is built using the task-based command line build tool [grunt.js](http://gruntjs.com) ([installation instructions](https://github.com/gruntjs/grunt#installing-grunt)). With Node.js and grunt.js installed, you need to start by running ```npm install``` in the reveal.js root. When the dependencies have been installed you should run ```grunt watch``` to start monitoring files for changes.
+reveal.js is built using the task-based command line build tool [grunt.js](http://gruntjs.com) ([installation instructions](http://gruntjs.com/getting-started#installing-the-cli)). With Node.js and grunt.js installed, you need to start by running ```npm install``` in the reveal.js root. When the dependencies have been installed you should run ```grunt watch``` to start monitoring files for changes.
 
 If you want to customise reveal.js without running grunt.js you can alter the HTML to point to the uncompressed source files (css/reveal.css & js/reveal.js).