Add details about GitX-dev fork in About menu

- Add fork name & tag line
- Update link to current github.io domain

This is what it looks like :

![gitxfork](https://f.cloud.github.com/assets/143380/726417/5fd66fcc-e0f5-11e2-94e2-943cb23617b8.png)

I think that would help figuring out which fork coworker are using until it is fully re-branded or renamed.