Remove outerHTML and createElementNS shims. Fixes #339

Not needed anymore, since we don't support <IE9
YUI app - convert to tabs
YUI app - code style improvements and HTML cleanup
Upgrade Backbone app to Backbone 0.9.9

- Update Backbone.localStorage
- Use `listenTo`
- Remove unused underscore file
Upgrade Backbone+RequireJS app to Backbone 0.9.9

- Update Backbone.localStorage and RequireJS
- Use `listenTo`
- Improve RequireJS config
Backbone apps - simplify `clearCompleted` logic