Update commenting guide.
Minor refine on guide
Merge branch 'master' of http://github.com/railsgirls-taiwan/railsgirls-taiwan.github.io

* 'master' of http://github.com/railsgirls-taiwan/railsgirls-taiwan.github.io:
  modified:   _includes/header.html
  modified:   _includes/header.html
  加入site.url 	modified:   _config.yml 	modified:   _includes/header.html
  加入OG title/description/img 加入RG3活動紀錄 	modified:   _includes/footer.html 	modified:   _includes/header.html 	new file:   _posts/2014-4-09-rg-taipei3rd-record.markdown 	new file:   images/RG2014LOGO500x500.jpg 	new file:   images/posts/rg3-all.jpg