This patch:
- resolves pending callbacks in connection once it gets closed
- fixes one of Page.screenshot() tests to wait for all the screenshots
- starts handling ECONNRESET error in test server to avoid throwing with no
good reason
This patch changes Page.navigate API:
- Page.navigate now resolves to the main page response
- Page.navigate throws errors if there's no main page response,
e.g. in case of SSL errors, max navigation timeout,
or invalid url.
This patch also adds httpsServer with a self-signed certificates
for the testing purposes.
Fixes#10.