Adds support for anchor links and adds heading anchor links

_Congratulations on the new site, by the way!_

Anchor links (#some-slug) didn't seem to pass the sanitation step, so I added a conditional to support it.

This PR also adds "Github style" heading anchor links. This way people can refer to specific part of the README (a anchor-icon is visible on heading hover). See image below.

I don't know if you are interested in this feature, but it's something I've been missing in the readmes, so I thought I'd give it a try.

![anchorlinks](https://cloud.githubusercontent.com/assets/606374/5381331/6e63c412-80a0-11e4-858a-208babcc590d.png)