Use epoch seconds to allow applying timezone offset

[blech]

I live in the US so the word clock example wasn't showing the right time. Now it does.

This is obviously not great, because it doesn't handle DST. But at least now there's a place to change it twice a year.

[blech]

I just noticed that vector_clock uses time.localtime() and that seems to do the right thing (although I'm not sure how). Maybe I'll look into that instead; it'd work around DST issues too.

[blech]

I also see that #28 includes time zone fixes as well as a bunch of other changes, so if you want to prefer that one, closing this is fine.

[blech]

Having read micropython/micropython#2130, never mind.