use redcarpet instead of maruku and enable autolink

the other redcarpet configuration options are stolen from
https://github.com/cklanac/jekyll-gfm/blob/master/readme.md
use consistent font for <code> blocks
use Lato as default sans-serif font

so that it looks consistent across mac and windows
add text shadow to post title
change "colors"image format from png to bmp

massive savings. png was 946 Bytes.  bmp is only 78 Bytes.
make octicons work for IE

needed to self host the octicons and add the X-UA-Compatible meta tag
which forces IE to use the most recent rendering engine.
new post: irssi and tmux quick start guide