todo-list: Add the functionality for listing todos.

It uses localStorage to save the todos temporary. when you clean the cache
all todos will be cleaned.
Enable add todo capability.
Add toggle all functionality.

When click on checkbox mark all, checked/unchecked all todo items.
Add a general style to the application.

create a general css "all.css". all css should be added to this file.
Note: don't add any css to index.html.
Add style to the header.

Add style to the title and the input.
add style to the todo list.
Merge branch 'style' into delivery