Requested updates to the Redis recipe

@rkneufeld I think that I have all the changes you requested done here.  Couple things of note:

* I am fully prepared to get taken apart on my implementation of `redis-memoize`.  I am completely open to a better solution, but this one works quite well for me.
* I did not add a pub/sub and message queue section yet.  I am happy to write them but this recipe is starting to feel long so I thought I would get it up as is and if you still want that I will go ahead and put it in.
* My prose feels awkward in a couple places.  If it is too terrible tell me and I will do my best.