[Design-team] Joining design team wiki page

[Emily Dirsh]

I've made a few updates to the 'how to join the design team' wiki page:
https://fedoraproject.org/wiki/Join_the_Design_Team 

Here's what I changed:
- I removed one of the info boxes that were at the top, and incorporated
it into the body of the article to remove a bit of clutter/confusion
- I cleaned up the writing a bit, clarified a few steps, and tried to
simplify things overall
- I mentioned the design bounties and pointed to Mo's blog (plug, plug,
plug - more ninjas!!!)
- That's it!

Check out the page history for the exact changes, and feel free to
revise/comment on any of the changes I made!

Emily