Development notice

Adds a yellow "development" environment notice to the Open Badges wordmark in the nav bar, with the git SHA as `title` if it's easy to determine.

<img src="http://f.cl.ly/items/3C2y1q1y2s1I28092S2T/Screen%20Shot%202013-02-01%20at%204.23.22%20PM%20%20%20%202-1-13.png">
(invisible mouse hovering on word 'development')