Add post for Sapporo.js-2013.05.19
Rewrite source in Gemfile

Because of avoiding the following warning:

```
The source :rubygems is deprecated because HTTP requests are insecure.
Please change your source to 'https://rubygems.org' if possible, or
'http://rubygems.org' if not.
```
Upgrade jekyll version to 1.0.2