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 Yes, that helps, thank you. 

@peterbe and @cvan Unfortunately, I still don't have an answer to my question about (possibly) specifying a content type with this:
```python
url(r'^(?P<path>contribute\.json)$', 'django.views.static.serve', {'document_root': settings.ROOT})
```
With that I'm getting Content-Type: application/octet-stream

![screen shot 2014-12-09 at 2 01 33 pm](https://cloud.githubusercontent.com/assets/1024066/5364782/119e9e5e-7fac-11e4-81f4-8e1b5514636e.png)

**Again, I removed the contribute view from mkt/site/views and am relying solely on django's static.serve view. I haven't pushed because I'm waiting to see if anyone can help me resolve this last issue.**

Sorry this is dragging on...I really appreciate the help! Let me know if what I'm asking needs further clarification.