docs(misc/Develop): update required Java version

Author: judytuna

docs/content/misc/contribute.ngdoc

@@ -31,7 +31,7 @@ development web server, run tests, and generate distributable files. Depending o
 pre-packaged bundle.
 
 * [Java](http://www.java.com): We minify JavaScript using our
-[Closure Tools](https://developers.google.com/closure/) jar. Make sure you have Java (version 6 or higher) installed
+[Closure Tools](https://developers.google.com/closure/) jar. Make sure you have Java (version 7 or higher) installed
 and included in your [PATH](http://docs.oracle.com/javase/tutorial/essential/environment/paths.html) variable.
 
 * [Grunt](http://gruntjs.com): We use Grunt as our build system. Install the grunt command-line tool globally with: