Added composer replace to fulfil swiftmailer/swiftmailer dependency by installing this package.

[thirsch]

What's your opinion on this? We could either replace swiftmailer/swiftmailer in symfony1's composer.json or add the replace-tag to this composer.json to tell composer that swiftmailer/swiftmailer ^6 is fulfilled by installing this package.

[thePanz]

Let's start with the "replace", than we can point symfony1 to this fork

Thank you for fixing the typo too ;-)