Purchase tickets call to action.

:space_invader: :fireworks: :space_invader: Add a better call to action for potential conference attendees to purchase tickets with a fixed banner at the top of every page. Looks like:

![screen shot 2014-03-18 at 5 34 40 pm](https://f.cloud.github.com/assets/316507/2454046/8b0048f8-aee5-11e3-8131-b7b5cdbd95a7.png)