Add sorl-thumbnail app for generating image thumbs
Thumbnail person photos

The team page is currently very slow to load as it loads several dozen
large high-quality images. Thumbnail these using sorl-thumbnail.

The images will be stored in S3 using django-storages, and details on
what thumbnails exist will be automatically cached in memcache using
django.core.cache.
Don't use absolute paths in gitignore

ag[1] doesn't like them.

[1]: https://github.com/ggreer/the_silver_searcher