duration in emails, various processor & filter tweaks

Used a separate redis connection in resque pikelets, as overloading on the resque one would return empty hashes unless two 'ok' events had previously been received for the check... very odd. This enables the duration check of the current state in the email to work OK.

I ran into problems testing the emails locally, but that persisted when I tried it with flapjack master as well. The data looks OK, I think it's something I need to fix on my laptop. (It was a bit hard to debug, EM just seems to drop the connection with nothing to log anywhere...)

There are also some changes to processor.rb and entity_check.rb to use transactions for those areas where multiple redis keys are written at the same time. I pass the entity check object into the filters to avoid it being looked up from redis multiple times, and changed the 'last_state' logic for notifications as well as I don't think that was previously doing what was expected.

Some of this probably needs discussion, I've been a bit below par this week so may well have the wrong idea on certain features...

Should fix #258 but has some other stuff too.