Merge pull request #1109 from SamyPesse/patch-1

Create GitBook.gitignore

GitBook.gitignore

+# Node rules:
+## Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
+.grunt
+
+## Dependency directory
+## Commenting this out is preferred by some people, see
+## https://npmjs.org/doc/faq.html#Should-I-check-my-node_modules-folder-into-git
+node_modules
+
+# Book build output
+_book
+
+# eBook build output
+*.epub
+*.mobi
+*.pdf