Date and time are now logged when KitchenTimer is stopped. Can be
queried as endedAt.
Fixed concurrency bug where the UI hangs when calling self.title() from
a thread other than the main thread. Tkinter expects all UI stuff to be
done in the same thread (the main thread).
Shorten default Pomodoro duration for faster system testing.
Reconciled whitespace.
Merge branch 'whenTimeup_hang'