Facebox chat link with guest / login options

Hey @sandal,

Here is that feature we discussed. It needs a little explanatory text, but I'm struggling to come up with something clear and concise. 

![Chat Facebox](https://f.cloud.github.com/assets/40662/2182198/c9fe27aa-977f-11e3-8a88-9ffdb8b64f7b.png)