Queue inherit form Sender to provide a fully compatible interface

Removed headers view, it is useless.
Emptied header view.

Signed-off-by: Guillaume Poirier-Morency <guillaumepoiriermorency@gmail.com>
Merge branch 'develop' of github.com:Hete/kohana-mail into develop

Conflicts:
	config/mail.php

Signed-off-by: Guillaume Poirier-Morency <guillaumepoiriermorency@gmail.com>