Bug 1007932 send vcard in an MMS

nit: we use this indentation convention in SMS:
```javascript
MimeMapper.guessTypeFromFileProperties(
  this.name,
  this.blob.type.toLowerCase()
);
```

Both arguments can be on the same line too, we're not strict about this. When there is 2 arguments it's still readable to have them on one line.

The idea is that the indentation count should never depend on a property or method name that can change over time. So we use this simple rule of always going to the next line and incremeting the indentation by 2 spaces.