add List class
add .all method to List class
refactor .search method for Task class
link tasks to respective list objects
add id to List class
refactor specs to use spec_helper
add .search_by_name method to List class
show list' tasks
update ui to reflect changes in List class
add list all tasks for a list
delete a list
add delete all tasks by list_id
update the interface to reflect delete tasks_by_list_id'
add marked_done method to Task class
update user interface to reflect marked_done
continue with due_date in task class