Adds output feedback when creating TODOs

[scalvert]

Resolves #66

When using TODO_DAYS_TO_WARN or TODO_DAYS_TO_ERROR without UPDATE_TODO, it prints the following error:

You must use UPDATE_TODO when using any of TODO_DAYS_TO_WARN or TODO_DAYS_TO_ERROR.
When new todos are created:

✔ 1 todos created

When new todo created with warn days:

✔ 1 todos created (warn after 10 days)

When new todo created with error days:

✔ 1 todos created (error after 10 days)

When new todo created with warn and error days:

✔ 1 todos created (warn after 5 and error after 10 days)

[renatoi]

LGTM