Authorization problem on node > 0.9.2

Starting node 0.9, the server certificate is validate by default, so an error is thrown : 
```
Error: Hostname/IP doesn't match certificate's altnames
```

To go back to previous behaviour, we can set the option `rejectUnauthorized` to `false`.

More explications here : https://github.com/mscdex/node-imap/issues/181