Add Facebook bot to testBot

Here are the Facebook crawlers User Agent:

```
FacebookExternalHit/1.1
FacebookExternalHit/1.0
```

or

```
facebookexternalhit/1.0 (+http://www.facebook.com/externalhit_uatext.php)
facebookexternalhit/1.1 (+http://www.facebook.com/externalhit_uatext.php)
```

Note that the version numbers might change.