Bug 982029 - [MMS/SMS] Display email in SMS/MMS Threads r=Julien

https://bugzilla.mozilla.org/show_bug.cgi?id=982029
please use this form:
```javascript
Contacts.findByAddress(..., function(...) {
  done(function() {
    assert.equal...
    .. other assertions
  });
});
```

Please do so for all new tests that are asynchronous (that use "done") in this file