Update example file dates

[alekwisnia]

It's not easy to check if 'navigate to today' feature works fine nowadays, so I've updated the dates in example file (index.html).

If you wish, here is the commit:
alekwisnia@c1b9aac
I'm new to github, I'd be glad if you guide me what's the best way to contribute.

[usmonster]

That's a good idea, thanks! Maybe even better if we had a function that generated the sample data (or that could be used to time-shift preset data), making sure that "today" was always within its range?

And you're going pretty good with your contributions so far, keep them coming!