Idle should interrupt pomodoro

[dracan]

Optionally, after a configurable amount of idle time, the Pomodoro should be interrupted.

For example, if you get pulled away from your desk, but forget to manually interrupt the Pomodoro - that shouldn't be allowed to complete and be logged as a successful Pomodoro.

[mattnield]

@dracan, what if you're on a web conf. or doing something that does not require computer interaction? Perhaps a dialogue to confirm whether that Pomodoro should be aborted would be an idea?