Doesn't close PhantomJS

My tests hang for a very long time. I think that calling `window.close()` will solve the issue. How are local non-headless browsers exited?

I've [added Electron support to launchpad](https://github.com/bitovi/launchpad/pull/80) and am running into this issue there as well. Inside its dev tools' console, I see that this error is being thrown:

```
Uncaught (in promise) Error: Timeout of 5000ms exceeded calling api/logs::create
```

…some time after running this line: https://github.com/bitovi/testee-client/blob/master/src/runner.js#L107

Though, even with the `this.call('logs', 'create'` line removed, the test runner still hangs.