Updating gems including official bootstrap-sass.

Twitter's official bootstrap-sass:
http://github.com/twbs/bootstrap-sass

It requires a small change in jekyll-assets:
https://github.com/ixti/jekyll-assets/pull/72

So currently using a modified version at:
https://github.com/yaegashi/jekyll-assets/tree/fix-asset-path-errors
Updating About page.
Adding a new post, fixing older posts.