add a contribute.json file (bug 1074452)

I did my best to find all the data to populate the json file, but l'm assuming I'll need to make a change or two. 
@peterbe When I said I'm thinking something's not right above, I was referring to my code, not the Air Mozilla stuff. Any idea why when I hit localurl/contribute.json the file downloads?

What is contribute.json being used for? I would assume that it's meant be consumed by some other service, maybe the docs...? If not, why json?