hologram configuration

I'm waiting on [this issue](https://github.com/trulia/hologram/issues/179) to be resolved and everything should be fine.
Funny to see that I discovered another bug in hologram because of a11y.css !

I dropped the index.md since it need to be in the sass/thems folder (that's another already reported bug in hologram). I think that's not really its place but maybe you want to put some text in for an intro page ?

Just run `bundle`and then `hologram`, and then serve the files from `tests` with `python -m SimpleHTTPServer`