Minor bug fix in controller.js Controller.prototype.removeItem

Controller.prototype.removeItem did not check if the item was available
via the DOM before calling removeChild.  If you were only viewing
"active" and clicked the "Clear completed" button it would result in an
error.  Wrapped the remvoeChild call in an if statement to validate
existence of the elememnt.
(vanilla)(jshint) Fix some errors.
Updated to ember v1.0.0 and ember-data v1.0.0-beta.1
Update to idiomatic ember 1.0:

 * Only auto-save todo when isCompleted changes, not when title changes
 * remove unused buttonClass:hidden
 * use .on('didInsertElement') in view
 * Remove 'text-cleared' sent action from EditTodoView,
   move auto-removal functionality into TodoController.
   Use debounce to prevent multiple calls to `removeTodo`
 * Save the todo in the `createTodo` action of TodosController
 * Put jshint globals declarations all on one line (valid jshint format,
 requested by todomvc)
Per the TodoMVC spec, cancel changes to a todo when escape is pressed.