adds in stanford s and creates a way for asset_urls to be defined

Closes #102 
Closes #61 

Using svg as progressive enhancement of png. I would also suggest this change in SW at some point.

Add a file `settings.local.yml` with the following

```
static_assets_url: 'http://127.0.0.1:3000/assets/'
```
Should compile the correct static asset url on precompile

#### ys688nq5480
![screen shot 2014-10-21 at 2 51 08 pm](https://cloud.githubusercontent.com/assets/1656824/4727451/9a99f39a-596c-11e4-9aa6-dbc6e8e26540.png)

#### tn148pd5374
![screen shot 2014-10-21 at 2 50 23 pm](https://cloud.githubusercontent.com/assets/1656824/4727452/9a9ee5f8-596c-11e4-97fb-12b385cf78c7.png)