Elixir on Xen blog post

/cc @alco @yrashk @georgeguimaraes @rafaelfranca @maximk

The goal is to publish it by thursday so Erlang on Xen team can announce it on Friday.

@maximk please let me know what you think and if you would like me to rewrite anything. You can [read the blog post here](https://github.com/elixir-lang/elixir-lang.github.com/blob/020f3ee78969fa5de5641cea93a24e3092121a81/_posts/2013-05-02-elixir-on-xen.markdown).