GSoC: finagle-smtp - initial

This is initial version of SMTP client for Finagle, which I am working on during GSoC'14.
For now it supports sending independent commands to SMTP server and sending a simple text email to one ore more addresses (without cc, bcc and reply-to). Usage is described in `README.md`. 
Ok, I've tried to use wireshark with QUIT sent in dispatcher, and it shows that the request is indeed not sent. The connection is just closed without even attempting to send it. Maybe I'm just doing it wrong? It appeared to me that I should override `close(deadline: Time)` method - is it right?