Merge branch '905-activities'

    Add Activity and Generator models which allow for
    activities to be created. This now works with the
    feed API.

diff --cc mediagoblin/db/migrations.py
Simple merge

diff --cc mediagoblin/db/models.py
Simple merge

diff --cc mediagoblin/federation/routing.py
Simple merge

diff --cc mediagoblin/federation/views.py
Simple merge

diff --cc mediagoblin/submit/lib.py
Simple merge

diff --cc mediagoblin/user_pages/views.py
Simple merge