Add activity model, polymorphic associations and tests
Create activities in controllers and add tests
Display activity feeds
Add pagination for activity feed
Add push updates
Add user gravatar after registration
Add more seeds
Add unblock friendship
Modify 'Add Friend' button depending on friendship status
Add tests for user unblock
Modify push updates to show 'You' for current_user
Clear push updates if user not authenticated
Change placeholder image on sign up page
Fix bug when changing profile avatar