Change grunt link to the project website. Closes jquery-validation#684

Has more useful getting started information for those unfamiliar with Grunt.

Author: nschonni

README.md

@@ -32,7 +32,7 @@ $("form").validate();
 For more information on how to setup a rules and customizations, [check the documentation](http://docs.jquery.com/Plugins/Validation).
 
 ## Contributing
-Follow the [jQuery style guide](http://contribute.jquery.com/style-guides/js), even if existing code doesn't. Add unit tests for any new or changed functionality. Lint and test your code using [grunt](https://github.com/gruntjs/grunt/).
+Follow the [jQuery style guide](http://contribute.jquery.com/style-guides/js), even if existing code doesn't. Add unit tests for any new or changed functionality. Lint and test your code using [Grunt](http://gruntjs.com/).
 
 If you've wrote custom methods that you'd like to contribute to additional-methods.js, create a branch, add the method there and send a pull request for that branch.