Fix connect URL with authentication.

Fix #13
On my system:
```bash
~/Repositories/mows (master)$ npm install testling -g
~/Repositories/mows (master)$ testling -u
MOWS server started on port 13097
http://localhost:53864/__testling?show=true

1..13
ok 1 MqttClient specifying a port should connect
ok 2 MqttClient specifying a port should publish and subscribe
ok 3 MqttClient specifying a port and host should connect
ok 4 MqttClient specifying a port and host should publish and subscribe
ok 5 MqttClient specifying a URL should connect
ok 6 MqttClient specifying a URL should publish and subscribe
ok 7 MqttClient specifying nothing should connect
ok 8 MqttClient specifying nothing should publish and subscribe
ok 9 MqttConnection specifying a port should publish and subscribe
ok 10 MqttConnection specifying a port and host should publish and subscribe
ok 11 MqttConnection specifying a URL should publish and subscribe
ok 12 mqttOverWs should expose MqttConnection
ok 13 mqttOverWs should expose MqttClient
# tests 13
# pass 13
# fail 0
```