testapp/scripts/web-server.js improvements

This simplifies the testapp webserver and instructions on running them. Let me know if the old handler for `x seccall` is needed:

```javascript
} else if (path.match(/\.\/(\d+)seccall/)) {
    var seconds = parseInt(path.match(/^\.\/(\d+)/)[1]);
    setTimeout(function() {
      res.write('done after ' + seconds + ' seconds');
      res.end();
    }, seconds * 1000);
    return;
  }
```

I didn't include it, and the test suite passes, so I just assumed it was leftover from the previous place `web-server.js` was brought in from.