Fixing Optimized Angularjs's markAll method.

Clicking the mark all checkbox in angularjs-perf currently sets all todos to be completed, but sets remaining count to todos.length instead of 0.  This can cause $scope.remainingCount to exceed todos.length and prevents the "Clear completed" button from displaying correctly.

![image](https://f.cloud.github.com/assets/274827/1971025/846f6c92-831d-11e3-875b-ef1eadb89c32.png)