Add new scoping features

Alright, here's the updated example application with the new features from

https://github.com/chrismccord/sync/pull/95

To demonstrate the new scoping features I added the user as an assignee to the todos. So a user now directly has many todos. I also added another test user and made the users show up in the navbar for easy switching.

The inline edit todo form now incorporates a user collection select field. That way one can see todos appearing and disappearing in different lists (in separate browser windows) when the assignee changes.

I switched to the 'autosync' model DSL for todos, users and projects. I left the CommentsController as is so that the manual way of syncing is still included.

Some other things I changed:

- added a database.yml since we are now using sqlite, so less setup is required
- cleaned up, removed old files
- added a second seed user to demonstrate scoping
- reduced number of seed todos for better overview

Once the 0.3.0 version is released, we should update the gem dependencies.

Hope you like the changes