Added the functionality to edit a item in the list.
Operations:
list (l) : Display all current items.
add (a) [item] : Add a new item.
remove (r) [id] : Remove an item by its ID.
edit (e) [id] [item] : Edit an item by its ID.
done (d) [id] : Toggle its done state by ID.
clear : Remove all items.
Full Changelog: 0.1.0-alpha...0.2.0-alpha