Throttle clients for some behaviours

[almet]

It's currently not clear what kind of behavior we want to have in case a client asks for the whole list of articles continuously. It seems to be a way to do a DDOS against the server.

Thanks to Videur, we can throttle the clients. We should also define the list of resources available, see https://github.com/mozilla-services/loop-server/blob/master/loop/api-specs.json for an example of how we did it for loop.

[almet]

We need to write the videur spec file and then open a bugzilla ticket with it!