req.baseUrl is more right for current express version (3.x)

app.mountpath for 4.x

this code is more reliable for following situation:
### express 4.x app with kue app (express 3.x)
```javascript
var express = require('express');
var app = express();
var router = express.Router();
var kue = require('kue');
router.use('/some/where/watchtower', auth.mid.requirePermission(Permission.TO.Watch), kue.app);
```

in case of upgrading kue's express 3.x to 4.x,
```javascript
res.redirect(app.mountpath + '/active');
```
in case of 
```javascript
res.redirect(req.baseUrl+'/active');
```
will be more durable.