WIP - added a middleware to dump all requests info into the stdout

the middlewares already contains [a logRequests feature](https://github.com/mozilla-services/loop-server/blob/master/loop/middlewares.js#L38-L51) middleware, and that's not really clear with the naming what this stdoutLog middleware does differently.

We probably should remove one of the two.
Also, this uses information from the responses (the status code) at a time where it doesn't have it yet. See how the mentioned middleware does.

+ it misses docs and tests ;)