Use real "Note" style for gist notes

Three of these in /gists

Before:

![screen shot 2014-05-12 at 13 27 54](https://cloud.githubusercontent.com/assets/211284/2943823/66387a90-d9c9-11e3-9ce9-e18348c072a7.png)

After:

![screen shot 2014-05-12 at 13 33 59](https://cloud.githubusercontent.com/assets/211284/2943825/761feff6-d9c9-11e3-9d0e-9f0a413da7c2.png)