Update mochajs documentation link.

sky/HACKING.md

 Hacking on Sky
 ==============
 
 Building
 --------
 
 * Follow the setup & build instructions for [Mojo](https://github.com/domokit/mojo)
 
 Running applications
 --------------------
@@ skipping 13 matching lines @@
 * ``sky/tools/run_sky_httpd``
 * ``out/Debug/mojo_shell --args-for="mojo:native_viewport_service --use-headless-config" --content-handlers=text/html,mojo:sky_viewer --url-mappings=mojo:window_manager=mojo:sky_tester mojo:window_manager``
 * The ``sky_tester`` should print ``#READY`` when ready
 * Type the URL you wish to run, for example ``http://127.0.0.1:8000/lowlevel/text.html``, and press the enter key
 * The harness should print the results of the test.  You can then type another URL.
 
 Writing tests
 -------------
 
 * Import ``resources/mocha.html`` and ``resources/chai.html``
-* Write tests in [mocha format](http://visionmedia.github.io/mocha/#getting-started) and use [chai asserts](http://chaijs.com/api/assert/):
+* Write tests in [mocha format](http://mochajs.org/#getting-started) and use [chai asserts](http://chaijs.com/api/assert/):
 ```html
 describe('My pretty test of my subject', function() {
   var subject = new MySubject();
 
   it('should be pretty', function() {
     assert.ok(subject.isPretty);
   });
 });
 ```
 
@@ skipping 13 matching lines @@
 
 Copying the file to googlestorage:
 $ sha1sum ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png
 db0508cdfe69e996a93464050dc383f6480f1283  ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png
 $ gsutil.py cp ../out/Debug/layout-test-results/framework/flights-app-pixels-actual.png gs://mojo/sky-pngs/db0508cdfe69e996a93464050dc383f6480f1283
 
 Long-term, we should not have these tests at all and should just
 dump paint commands. In the short-term, if we find we're doing this
 a lot we should obviously automate this process, e.g. test_sky could
 do all of this work, including spitting out the correct reference file.