Add some notes about deployment to production

This is definitely a first cut, and I hope you'll give me some feedback; I'll change it as necessary.

I added three sections:

* Serving in production - tells the user the parts they should be deploying, and suggests ways they might serve each
* Example upstart scripts - what it says on the tin. Even if users don't use upstart, the scripts should help them figure out how they ought to run the plugins and the bot on their system.
* Running in a subdirectory - a brief note about what I had to do to run botbot in a subdirectory. Not sure if this is useful or not?

Hope this is helpful, and not just a pain.