default dbname is invalid.

[sugyan]

MongoStore's constuctor options can use "server_config" instead of "db".
but default dbname is "/dev". this is invalid name for mongodb.

https://gist.github.com/1102625

  , _defaults = {host: '127.0.0.1', port: 27017, dbname: '/dev', collection: 'sessions', reapInterval: 60 * 1000};

maybe it's from 0.x, mongodb connnection used "mongodb://host:port" + dbname style URL.

 url += (hosts[i] || hosts[0]) + ':';
 url += ports[i] || ports[0];
 url += options.dbname ? '/' + options.dbname : defaults.dbname;

but now 1.0.x, connect-mongodb doesn't use this URL. so default dbname should "dev" (exclude slash).