Move ShoppingList model to ShoppingListItem

I had misunderstood the tutorial content.
Add ShoppingListItem fixtures
Add ShoppingListItem model data to main template
Refactor ShoppingList item model

Move isPending attribute to isDone in order to make bindings simpler.
Revert "Refactor ShoppingList item model"

This reverts commit c195a1e34370940090cea43530b5a5fb3df8c0ab.

I found how to use the isPending attribute to set the .done class :)
See http://emberjs.com/guides/templates/binding-element-class-names
Fix router reference to model, rename app
Fix ShoppingListItem model, follow naming conventions
Add ShoppingListItemsController
Add shopping list items status to main template

This commit contains interesting examples of attribute binding.
Fix ShoppingListItem creation

Remove the form tag which prevented the `enter` key event to trigger
ShoppingListItems creation.

Minor stylesheet fix for Chrome, remove input outline