update: Changed Gitbook links was updated.

Author: amarouter

translation_howto.md

@@ -3,6 +3,6 @@
 1. The full source of the book is available from {{ book.sourceUrl }}.
 2. Please [fork the repository](https://help.github.com/articles/fork-a-repo).
 3. Then, fetch the repository to your computer. You need to know how to use [Git](http://www.git-scm.com) to do that.
-4. Read the [GitBook documentation](https://help.gitbook.com), esp. the [Markdown section](https://help.gitbook.com/format/markdown.html).
+4. Read the [GitBook documentation](https://docs.gitbook.com), esp. the [Markdown section](https://docs.gitbook.com/editing-content/markdown).
 5. Start editing the `.md` files to translate to your local language.
 6. [Sign up on GitBook.com](https://www.gitbook.com), create a book and you can see a beautifully rendered website, with links to download PDF, EPUB, etc.