Messed up Mailer (Introduced by 4.1 -> 4.2)

In 4.1 it was possible returning a count of sent emails from Mail::send().
In 4.2 you'll always get null returned. 
(`Mail::send()` is now returning the `void` method `sendSwiftMessage()`)

> `sendSwiftMessage()` was returning a count of sent emails in 4.1

If that was intended the send method needs an update which I'm providing with this pull request.
Anyways I hope it was not and the `send()` method will return the count of sent emails again in future. (Was using this feature and liked it alot)

__EDIT__
This Pull Request is just fixing a wrong PHPDoc block for `Mail::send()`. Please don't get confused by my writing above :-)