Register button on devhub (bug 1095659)

WIP: still some touchups to do.

![sign-in-up mov](https://cloud.githubusercontent.com/assets/211578/4961774/fe1abd78-66d2-11e4-9fd9-17f66867526d.gif)

This had no affect. Since the pseudo-element is treated as being inside the `<a>` it gets its `font-size` set to `13px` like the link. Setting it on the pseudo-element doesn't take away the clickable area. I think I'll need to wrap the `<a>` in a `<div>` instead of doing `:before` or `:after`.