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`. 
This might also be more idiomatic if you destructured it like this:

```scala
val arr: Array[String] // we've already checked it's of length 2
val Array(first, second) = arr
```