Fix the outdated link of google's java style guide

Closes #330

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=161601413

Author: tianyin

CONTRIBUTING.md

@@ -42,6 +42,6 @@ Code cannot even be evaluated without this step.
 
 [CLA]: https://cla.developers.google.com
 [forking]: https://help.github.com/articles/fork-a-repo
-[java style guide]: http://google-styleguide.googlecode.com/svn/trunk/javaguide.html
+[java style guide]: https://google.github.io/styleguide/javaguide.html
 [well-formed commit messages]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
 [pull request]: https://help.github.com/articles/creating-a-pull-request