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`. 
I don't think `service(Request.Quit) before service.close(deadline)` will work, because we want to close even if we can't Quit properly, but maybe `ensure` would be the right semantic.  Can you use wireshark and check that the tcp connection is actually being torn down when you expect it to be torn down?