add about page
start work on profile page

- caffeine.models:
  - implement CaffeineManager with method total_caffeine_for_user and use it
    as Caffeine.objects
- caffeine.templatetags.caffeine:
  - implement a template tag publicurl to provide the absolute URL of a
    user's public profile
- caffeine.urls:
  - define new URLs ontherun, ontherunold and submit_caffeine
- caffeine.views:
  - add get and get_context_data methods to ProfileView
  - implement OnTheRunView as TemplateView
  - implement OnTheRunOldView as RedirectView to redirect clients using the
    old URL pattern to OnTheRunView
  - implement dummy SubmitCaffeineView
- templates/base.html: cosmetics
- templates/profile.html: start of profile page template