Followup to 2b995142

It's now in the Wiki:
https://github.com/addyosmani/todomvc/wiki/Other-implementations

#203

Improvements in Backbone.js application

Here my modifications to respect the "best-pratices" in Backbone.js :

**Model** - js/models/todo.js

 - remove `initialize` method in Model (useless because `defaults` do already the job)
 - remove `clear` method, we should not change `clear` behavior of Backbone.Model -> http://backbonejs.org/#Model-clear

**Views** - js/views/app.js and js/views/todos.js

 - Call model.destroy() (model.clear(); is not logic)
 - Use this.$el instead of $(this.el) to improve readability and caching

Correct this issue: https://github.com/addyosmani/todomvc/issues/223 with adding `window.app.Todos.on( 'change:completed', this.addAll, this );` and `add` event call now `addAll` method in *js/views/app.js*

Issue related too: https://github.com/addyosmani/todomvc/issues/253

Ember+Require app: Apply the fix from Ember app for showing selected filter in the filter bar. Fixes #220

- Cleanup
- Code style
- Fix bug with removing todo after editing and the todo is empty
- Update dependencies

fixed broken HTML structure

fix broken link to epitome home page from todo page

YUI - Title and credits fix for consistency

Fixes CanJS Demos, removes Zepto.

refactor for code style, spaces creep in, fix issue with active filter, ...

refactor for code style, spaces creep in, fix issue with active filter, change completed to boolean, editing enter fires blur, see pull/235#issuecomment-7264416

Site: Add checkmark list-style to whats new, Twitter and G+ buttons, and Twitter and Open Graph meta tags