Canjs 1.1.3 + RequireJS

Here is the updated and cleaned up CanJS 1.1.3 + RequireJS example as discussed in #254:

- Implemented comments from code review
- Todos are filtered on the model level
- Follows code style and JSHint
- Update to CanJS 1.1.3
- Uses jQuery and RequireJS from assets folder
- Fixed "Clear completed" button
- Included readme as discussed
- Added example to readme and site