First implementation of PHPMailer.
Improved testing using a sender provider.
Merge remote-tracking branch 'origin/3.3/develop' into 3.3/feature/PHPMailer

Conflicts:
	classes/Kohana/Mail/Sender.php
	tests/MailTest.php
Update README.md

Updates the documentation to specify support for PHPMailer.
Update README.md
Fixes PEAR mailer when using attachments.
Updates composer.json for PHPMailer.
All tests run for PHPMailer!
Exposing the PHPMailer instance.
Merge branch '3.3/feature/PHPMailer' of https://github.com/Hete/kohana-mail into 3.3/feature/PHPMailer