Add method to mark a list as completed from TodoList.

This will mark the todo list dirty.

TodoList.py

@@ -280,6 +280,11 @@ class TodoList(object):
     def todos(self):
         return self._todos
 
+    def set_todo_completed(self, p_number):
+        todo = self.todo(p_number)
+        todo.set_completed()
+        self.dirty = True
+
     def __str__(self):
         return '\n'.join(pretty_print(self._todos))
 

test/TodoListTest.py

@@ -142,6 +142,10 @@ class TodoListTester(unittest.TestCase):
         self.assertIsInstance(todo, Todo.Todo)
         self.assertEquals(todo.text(), "No number")
 
+    def test_todo_complete(self):
+        self.todolist.set_todo_completed(1)
+        self.assertTrue(self.todolist.todo(1).is_completed())
+
 class TodoListDependencyTester(unittest.TestCase):
     def setUp(self):
         self.todolist = TodoList.TodoList([])