Add ``Thumbnailing`` support.

https://github.com/madewithbytes/us_ignite/issues/82

The component used to generate thumbnails is ``easy_thumbnail``.

Supports S3 Storage for the generated thumbnails.

See http://easy-thumbnails.readthedocs.org/en/latest/ for more
configuration details.
Add thumbnail to application detail.
Add thumbnails accross detail pages.

https://github.com/madewithbytes/us_ignite/issues/82

Basic templates have been added to the detail pages.