* Site: New _get_logged_in_user() method, name self-explanatory. This acts
  as a replacement for the former crud in get_user(), which now calls this
  when the username arg is None. This method will first try to determine
  our username based on a special cookie in self._cookiejar (cookie.name is
  self._name + "UserName", e.g. "enwikiUserName"), and will only do an API
  query if no cookie was found. This removes an API query that is usually
  only necessary if we are not logged in.
* Site: silly bugfix in __init__().
* User: Reverted earlier change to _get_attribute() (addition of
  raise_exception arg); name() and exists() now use their own code, which
  is simpler.
* User: Calling name() does not do an API query unless force=True, unlike
  the other "get" methods.
* User: .join() instead of .format() because I feel it looks cleaner and is
  probably more efficient.