update(update, callback) {
		const id = update.id;
		const todos = this.getLocalStorage();
		let i = todos.length;
		let k;

		while (i--) {
			if (todos[i].id === id) {
				for (k in update) {
					todos[i][k] = update[k];
				}
				break;
			}
		}

		this.setLocalStorage(todos);

		if (callback) {
			callback();
		}
	}
Update an item in the Store.

@param {ItemUpdate} update Record with an id and a property to update
@param {function()} [callback] Called when partialRecord is applied