Fix whilst setup and solution

This should fix https://github.com/bulkan/async-you/issues/9

I think there a variety of issues with `whilst`, running on my local machine, I noticed:

 - the server is not restarted between running the student's solution and the suggested solution, so their requests can interfere with each other. The server could be waiting for 5 reqs before responding with `meerkat`, and get 3 from the student's solution and 2 from the suggested solution, both will end up with the wrong answer!
 - the current suggested solution always returns 2 because it starts a tiny bit later than the student's solution, when the server has (almost always) started returning `meerkat` already, so it just counts 1 `data` event plus the initial value of 1.

We can get around the solution interference problems by starting two servers, and returning an object from `setup.js` with both `submissionArgs` and `solutionArgs`, instead of just `args`.

For fixing the solution itself, I think we should start with `count = 0;` and increment either at the start or end of a request.