Implement repeating feature.

Repeating feature is needed to improve usability. The feature will be used like:

```
down 5:00 up 10 repeat 3
```

The commands above starts countdown for 5 minutes and countup for 10 seconds, then repeats those two three times.

The commands below

```
down 5:00 up 10 repeat
```

starts countdown for 5 minutes and countup for 10 seconds, then repeats those two until the user stops.