Internet explorer 9 support for the API

[rammie]

I recently ran into this in production. If you like the fix, I can put together a pull request, though it's just a couple of lines. I had to add cache control headers to the response to prevent the great IE9 from caching ajax requests.

class RestResource(RestResource):
...
def response(self, data):
kwargs = {} if request.is_xhr else {"indent": 2}
resp = Response(json.dumps(data, **kwargs), mimetype="application/json")
resp.headers["Cache-Control"] = "no-cache, no-store, must-revalidate"
resp.headers["Pragma"] = "no-cache"
resp.headers["Expires"] = 0
return resp