fixes

- do not add new item if empty (probably better way to do this)
- link toggle to item.completed
Pluralize items left
First attempt to provide routes
better use of ng-class
remove '0' in ng-pluralize as it can be considered as 'other'
show #main and #footer only if todo list is not empty
Start implementing remaining count of todos
add editing class after double clicking on item. Add method that determines how many remaining todo items there are
remove todos when clicking on the cross
change class on filter depending on route