docs(README.md): add note about JDK requirement

Author: gkalpak

README.md

@@ -21,7 +21,7 @@ The full tutorial can be found at https://docs.angularjs.org/tutorial.
 
 ### Node.js and Tools
 
-- Get [Node.js][node-download].
+- Get [Node.js][node].
 - Install the tool dependencies: `npm install`
 
 
@@ -190,7 +190,7 @@ it whenever you like.
 
 - Run `npm start`.
 - Navigate your browser to [http://localhost:8000/](http://localhost:8000/) to see the application 
-- running.
+  running.
 
 ### Unit Testing
 
@@ -216,6 +216,13 @@ _Running the Application during Development_ section, above.
   set up to run the tests on Chrome directly. If you want to run against other browsers, you must 
   modify the configuration at `e2e-tests/protractor-conf.js`.
 
+**Note:**
+Under the hood, Protractor uses the [Selenium Standalone Server][selenium], which in turn requires 
+the [Java Development Kit (JDK)][jdk] to be installed on your local machine. Check this by running 
+`java -version` from the command line.
+
+If JDK is not already installed, you can download it [here][jdk-download].
+
 
 ## Application Directory Layout
 
@@ -260,10 +267,13 @@ For more information on AngularJS, please check out https://angularjs.org/.
 
 [angular-seed]: https://github.com/angular/angular-seed
 [bower]: http://bower.io/
-[git-home]: https://git-scm.com
-[git-setup]: https://help.github.com/articles/set-up-git/
-[google-phone-gallery]: http://web.archive.org/web/20131215082038/http://www.android.com/devices/
+[git-home]: https://git-scm.com/
+[git-setup]: https://help.github.com/articles/set-up-git
+[google-phone-gallery]: http://web.archive.org/web/20131215082038/http://www.android.com/devices
 [jasmine]: https://jasmine.github.io/
-[karma]: https://karma-runner.github.io
-[node-download]: https://nodejs.org/en/download/
+[jdk]: https://wikipedia.org/wiki/Java_Development_Kit
+[jdk-download]: http://www.oracle.com/technetwork/java/javase/downloads
+[karma]: https://karma-runner.github.io/
+[node]: https://nodejs.org/
 [protractor]: http://www.protractortest.org/
+[selenium]: http://docs.seleniumhq.org/