Changes to comply with more xmpp server implementations:

Without the first change, on at least 2 jabber servers I've tried (jabberd and OS X builtin) the handler joins the room, but no messages appear.

Without the second change a random nick is appended to the jid (xmpp_jid) when the user joins/leaves the room - e.g.:

```
sensu [sensu@foo.example.com/928793f28fc90ec46c85ea0e9a309fd0917ea2e2] entered the room.
```

After the patch:

```
sensu [sensu@foo.example.com] entered the room.
```