Use only the path component of STATIC_URL as the folder name on the CDN

The command

    ./manage.py syncstatic

uploads assets to the CDN, storing them in the folder with the same name as STATIC_URL.
By default STATIC_URL is `/static`, so the assets are uploaded to http://cdn-url/static/

However, `settings.STATIC_URL` can also be a **full URL**, for instance http://akamai.net/static.
In this case, `./manage.py syncstatic` would upload the assets to http://cdn-url/http://akamai.net/static.

My commit extracts the **path** component from STATIC_URL and uses that as the folder name on the CDN.
The result is that, in both of the previous cases, the assets would be uploaded to http://cdn-url/static