Add Simplified Chinese version of learnyounode && add new selectors

* Add Simplified Chinese version of learnyounode 
* Add `menu-tutorials ` selector in index page
* Fix previous selector `.index header h3` which selected two `h3` elements
* Add new selector to select newsletter `h3` element
* Fix selectors in Workshoppers section in index page, which caused by  added `View Workshopper List`  link
* Add new selector to select the new workshop `learnyoucouchdb `
* Add selector to select the text about `edit an event you've submitted` in event page

BTW: 

* All new selectors that I added, is already for Simplified Chinese, and won't mess up other languages. It's safe to merge.
* We should think about a better way for update. Because, just like the issue about the Workshoppers section which I described above, when we update a .html file. the css selectors may be changed. It will cause unexpected problem in other languages.