fixed ServiceNotFoundException for dependency on 'swiftmailer.transport.buffer'
bug #75 fixed ServiceNotFoundException for dependency on 'swiftmailer.transport.... (acin91)

This PR was merged into the 2.3-dev branch.

Discussion
----------

fixed ServiceNotFoundException for dependency on 'swiftmailer.transport....

This PR is the fix for exception which occur when transport is sendmail

```
[Symfony\Component\DependencyInjection\Exception\ServiceNotFoundException]
  The service "swiftmailer.mailer.default.transport.real" has a dependency on a non-existent service "swiftmailer.transport.buffer".
```

Commits
-------

70fcc73 fixed ServiceNotFoundException for dependency on 'swiftmailer.transport.buffer'