Added option to set number of pomidori before long break.

Hi,

Sorry if I'm not doing this correctly, this is the first time I've used GitHub and I'm trying to follow the tutorials as best I can. I added this mod to my own desktop timer (after some hacking; I don't actually know javascript) and thought I'd mention it in case it's of any interest. It just adds a setting to choose how many pomidori run before a long break; presumably you could write this much better but I thought this might be the best way to suggest it as a feature.

Thanks,

stellarpower