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`. 
thinking about java compatibility, default arguments make this really hard to use from java.  I think it's fine to keep these, but could you make a couple other nice builder methods that can be used from java?  Maybe something that doesn't take any arguments.