When a task changes types, reset all attributes as if it were created from scratch

[kusold]

See #23 for more information (when Alys jumps into the conversation)

[crookedneighbor]

Note that in the current version of the API that you cannot change one type of task to another. If the module wants to do that, it'll have to remove the original task from Habit, remove the json data for the habit task from .todoist-history, and create a new task of the new type and save that to .todoist-history