Remove return statement when there is no user on the cookie

This is so we can check if they are logged in on the "way out" and update memcached
accordingly
Check for req._userJSONCopy as well as oldSessionUser

This is because when logging in, the oldSessionUSer will exist but the userJSONCopy
not, this is how we can tell if this request is a login.
Check for lack of original username and presence of a user objetc on the session

We use the sessionBeforeBlack list to avoid missing values from our blacklisted
cookies which happen high in the stack. If there was no original username, and
there is a req.session.user now, we know that the user has just logged in, so we
set them to memcached, knowing that the data just came from mysql
Reformat else if indentation
Refactor the logic for setting to memcached.

First we've renamed the oldSessionUser variable to sessionUser, as that
is most accurate in what we're actually doing. The logic implemented is
as follows:

  - If there's no user on the session - don't save!
  - If there *is* a user on the session, and the data is the same as what
    we have in memcache already - don't save!
  - For everything else - save it.
Merge pull request #1567 from jsbin/fix/memcached

Fix/memcached