BREAKING CHANGE: some methodes in Event and MoonPhase have been dropped
in favor of `enum.Enum`'s `name` and `value` properties.

Using Ctrl+C to interrupt the program won't display a big ugly error
anymore.

BREAKING CHANGE: invoking kosmorro command without --latitude and
--longitude arguments will now only output the Moon phase and,
eventually, the events for the given date (or today if date not given).

BREAKING CHANGE: invoking kosmorro command with the --altitude argument
will now fail with an "unrecognized arguments" error.