add entry list to profile page

- caffeine.models:
  - implement CaffeineManager.latest_caffeine_for_user
  - implement Caffeine.format_type
- caffeine.urls:
  - add URL for DeleteCaffeineView
- caffeine.views:
  - add latest caffeine entries to context of ProfileView
  - add dummy DeleteCaffeineView
- templates/profile.html:
  - add block to output caffeine entries