Clean up Get Involved CSS
Clean up the get involved box code

- Use a common `.getInvolvedBox` class
- Reduce code duplication
- Fully scalable
Clean up sprite32.png

@veosotano: Remain calm. No need to freak out. We'll have a generator
up and running soon. Maybe not next week, because all hell is about
to break loose, but sometime soon.
Fix latest blog posts' links

Close #446