record WIP, expose fetchUser to user opts

Make fetching user profile metadata configurable via server opts.
Some users may for whatever reason want to do this:

    function fetchUser (name, next) {
      var profile = { name: name };
      // myProfileLookup(profile, next);
      next(profile);
    }
    var opts = {fetchUser: fetchUser};
    server = createServer(opts);

Simplest way is to just listen for:

    server.event.on('profile', function (hook, next) {
      // hook.map(...)
      next( );
    });