Post layout

This add:

- adds .gitignore for generated `_site` folder
- a blog post layout that matches the existing blog feed layout
 - with title, date, author
- padding so that posts don't hit the edge of the page

**blog feed page**
![screen shot 2014-04-01 at 5 47 40 pm](https://cloud.githubusercontent.com/assets/1305617/2586435/7ec955e0-ba00-11e3-89e4-a609b4462206.png)

**blog single post page**
![screen shot 2014-04-01 at 5 47 44 pm](https://cloud.githubusercontent.com/assets/1305617/2586443/98006b20-ba00-11e3-8f8e-96ed88f00476.png)

:) :cat2: