[HTTPS-Everywhere] separate rules from addon

[Osama Khalid]

Peter Eckersley:
> We could try to release more often, or we could have a nightly git
> branch of the extension, or we could have the rules updated
> separately, and all of these would have the effect of moving both
> bugfixes and new bugs make into people's browsers faster :).

That's a very good point. I think rules should have a better way for
updating other than updating the whole addon on startup which's,
i.e. the too frequent, unsilent updates, to some people one of the
most annoying things about Firefox and its addons.

--Osama Khalid