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`. 
The definition of `From` field is this:
   from            =   "From:" mailbox-list CRLF
I understand it so that the name of this field should start with a capital letter.