Name change: or -> tor

[Roger Dingledine <arma@mit.edu>]

Too many people have been telling me lately that 'or' is too generic. "I'm
building onion routing." "Oh, really, which one?" "No, I'm building the
onion routing design." "Yeah, I know, which one?"

But we really are building *the* onion routing design; not just another
spin-off design.

And so I dub us tor -- the onion router.

Besides, now we can talk about the system in text without looking like
we never learned how to use conjunctions properly.

--Roger