REST API's for todo app
#GET : /list ==> return all the tasks
#POST : /insert ==> creates a new task
#DELETE : /list/id ==> deletes the task with the specified id
#PUT : /list/id ==> updates the task with the specified id
#GET : /save ==> saves all the created tasks in todos.json
#GET : /load ==> loads all the saved tasks from todos.json